HomeSearch by dateVacation packagesHotelsFlight dealsCar rentalTravel tips & news
Guatemala

$100+ Cheap flights from Newark (EWR) to Guatemala

This is the cheapest one-way flight price found by a Cheapflights user in the last 72 hours by searching for a flight departing on 2/8. Fares are subject to change and may not be available on all flights or dates of travel.
EWR — GUA
Nov 16 — Nov 231
Sun 11/16
Sun 11/23
1 adult, Economy
We work with more than 300 partners to bring you better travel deals

Find cheap flights from Newark to Guatemala with Cheapflights

1. Tell us where you want to go

Enter your travel information like dates, passengers, trip type (one-way or round trip), and preferred cabin class then click “Find deals”

2. Select your favorite providers

We find the providers serving your travel needs. Choose up to four travel providers to compare side-by-side for flights, hotels, or car rentals.

3. Compare prices and book

Review each provider’s pricing and select the best option for you! Book through your favorite provider’s website for a seamless experience.

Cheap flight deals from Newark to Guatemala

Keep the following information in mind while searching for Newark to Guatemala flight deals. Data was last updated October 17, 2025.

Most accurate provider

FlightHub
3 stars

Most trusted provider

FlightHub
3 stars

Round-trip from

$195
(Cheapflightsfares)

One-way from

$100
(SmartFares)

Popular in

December

Cheapest in

September

Average price

$318

Good round-trip deal

$290 or less

Good one-way deal

$133 or less
Provider with most accurate pricing for New York (NYC)-Guatemala City La Aurora flight deals.
Search Deals
Provider most trusted by Cheapflights users for New York (NYC)-Guatemala City La Aurora flights.
Search Deals
From Newark to Guatemala
Search Deals
One-way flight from Newark to Guatemala
Search Deals
Highest demand for flights based on searches. 21% potential increase in price ($113 potential increase over avg. RT price).
Search Deals
Cheapest flight prices on average. 6% potential price decrease ($24 potential savings vs. average RT price).
Search Deals
Average for round-trip flights in October 2025
Search Deals
Price to beat on a round-trip flight from Newark to Guatemala.
Search Deals
Price to beat on a one-way flight from Newark to Guatemala.
Search Deals

Find flight deals from Newark to Guatemala

Cheapest flights from Newark to Guatemala
Explore the most affordable flight options available from Newark to Guatemala. Find the lowest fares from popular airlines and budget airlines, with prices last updated on October 17, 2025.

This Cheapflightsfares deal was found by Cheapflights users on 10/15. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Cheapflightsfares is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 11/116:38 amEWR - GUA
1 stop6h 48mSpirit Airlines
Mon 11/171:31 pmGUA - EWR
1 stop7h 55mSpirit Airlines
Deal found 10/15$195
This Cheapflightsfares deal was found by Cheapflights users on 10/16. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Cheapflightsfares is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 11/125:14 amEWR - GUA
1 stop7h 07mSpirit Airlines
Wed 11/121:31 pmGUA - EWR
1 stop7h 55mSpirit Airlines
Deal found 10/16$204
This Booking.com deal was found by Cheapflights users on 10/15. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Booking.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 11/56:38 amEWR - GUA
1 stop6h 48mSpirit Airlines
Wed 11/121:31 pmGUA - EWR
1 stop7h 55mSpirit Airlines
Deal found 10/15$211
This Cheapflightsfares deal was found by Cheapflights users on 10/15. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Cheapflightsfares is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Mon 11/106:38 amEWR - GUA
1 stop6h 48mSpirit Airlines
Wed 11/121:31 pmGUA - EWR
1 stop7h 55mSpirit Airlines
Deal found 10/15$214
This CheapOair deal was found by Cheapflights users on 10/16. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure CheapOair is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 11/125:14 amEWR - GUA
1 stop7h 07mSpirit Airlines
Wed 11/191:31 pmGUA - EWR
1 stop8h 58mSpirit Airlines
Deal found 10/16$216
This Cheapflightsfares deal was found by Cheapflights users on 10/16. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Cheapflightsfares is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 11/125:14 amEWR - GUA
1 stop7h 07mSpirit Airlines
Tue 11/181:31 pmGUA - EWR
1 stop7h 55mSpirit Airlines
Deal found 10/16$217
This Expedia deal was found by Cheapflights users on 10/16. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Expedia is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 11/116:38 amEWR - GUA
1 stop6h 48mSpirit Airlines
Tue 11/181:31 pmGUA - EWR
1 stop7h 55mSpirit Airlines
Deal found 10/16$226
This Cheapflightsfares deal was found by Cheapflights users on 10/17. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Cheapflightsfares is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 11/56:38 amEWR - GUA
1 stop6h 48mSpirit Airlines
Thu 11/131:31 pmGUA - EWR
1 stop9h 40mSpirit Airlines
Deal found 10/17$227
This Cheapflightsfares deal was found by Cheapflights users on 10/15. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Cheapflightsfares is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 11/126:38 amEWR - GUA
1 stop6h 48mSpirit Airlines
Tue 11/251:38 pmGUA - EWR
1 stop9h 53mSpirit Airlines
Deal found 10/15$230
This Mytrip deal was found by Cheapflights users on 10/16. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Mytrip is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 11/156:38 amEWR - FRS
2 stops14h 37mMultiple Airlines
Sat 11/2210:40 amFRS - EWR
2 stops12h 51mMultiple Airlines
Deal found 10/16$432
This Mytrip deal was found by Cheapflights users on 10/16. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Mytrip is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 11/66:32 pmEWR - FRS
2 stops23h 43mMultiple Airlines
Sun 11/97:20 amFRS - EWR
3 stops27h 48mMultiple Airlines
Deal found 10/16$495
This Mytrip deal was found by Cheapflights users on 10/17. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Mytrip is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Mon 11/249:00 pmEWR - FRS
2 stops23h 50mMultiple Airlines
Fri 11/287:45 amFRS - EWR
2 stops15h 46mMultiple Airlines
Deal found 10/17$518

Cheapflights Fare Finder

 
Customize your flight search to find flights from Newark to Guatemala that fit within your specific budget. Explore options based on user searches and filter the results based on your desired price range. Find flights that match your budget for a cost-effective journey. Over the last 7 days, Cheapflights users made 2,558,603 searches. Data last updated October 17, 2025.
Use the filters below to find and compare flights from Newark Airport to Guatemala that are best for you.

Fly from

Newark

Fly to

Guatemala

Route

Depart

Return

Price

NewarkGuatemala City

EWR - GUA

EWRGUA

Newark

Thu 1/29

6:34 pm-10:48 pm

Nonstop5h 14m

Guatemala City La Aurora

Sun 2/1

11:59 pm-5:30 am

Nonstop4h 31m

$229

NewarkGuatemala City

EWR - GUA

EWRGUA

Newark

Wed 1/21

6:34 pm-10:48 pm

Nonstop5h 14m

Guatemala City La Aurora

Mon 1/26

11:59 pm-5:30 am

Nonstop4h 31m

$268

NewarkGuatemala City

EWR - GUA

EWRGUA

Newark

Wed 11/12

6:34 pm-10:48 pm

Nonstop5h 14m

Guatemala City La Aurora

Wed 11/19

11:59 pm-5:30 am

Nonstop4h 31m

$269

NewarkGuatemala City

EWR - GUA

EWRGUA

Newark

Fri 1/9

6:15 am-7:39 pm

1 stop14h 24m

Guatemala City La Aurora

Sun 2/8

11:59 pm-5:30 am

Nonstop4h 31m

$278

NewarkGuatemala City

EWR - GUA

EWRGUA

Newark

Sun 2/22

6:34 pm-10:48 pm

Nonstop5h 14m

Guatemala City La Aurora

Thu 2/26

2:10 am-12:59 am

1 stop21h 49m

$306

NewarkGuatemala City

EWR - GUA

EWRGUA

Newark

Wed 2/18

6:34 pm-10:48 pm

Nonstop5h 14m

Guatemala City La Aurora

Mon 2/23

5:00 am-12:59 am

1 stop18h 59m

$306

NewarkGuatemala City

EWR - GUA

EWRGUA

Newark

Mon 11/3

6:34 pm-10:48 pm

Nonstop5h 14m

Guatemala City La Aurora

Wed 11/12

11:59 pm-5:30 am

Nonstop4h 31m

$318

NewarkGuatemala City

EWR - GUA

EWRGUA

Newark

Wed 11/5

6:34 pm-10:48 pm

Nonstop5h 14m

Guatemala City La Aurora

Thu 11/6

1:05 am-10:05 am

1 stop8h 00m

$328

NewarkGuatemala City

EWR - GUA

EWRGUA

Newark

Tue 11/25

6:34 pm-10:48 pm

Nonstop5h 14m

Guatemala City La Aurora

Tue 12/2

1:05 am-10:05 am

1 stop8h 00m

$330

NewarkGuatemala City

EWR - GUA

EWRGUA

Newark

Thu 11/13

6:34 pm-10:48 pm

Nonstop5h 14m

Guatemala City La Aurora

Wed 11/19

1:05 am-10:05 am

1 stop8h 00m

$330

Flights are sorted by cheapest round-trip flights first.

Deals found on 10/16

Showing 1-10 of 28 results
1
2
3

Best time to book a flight from Newark to Guatemala

Have a flexible travel schedule? Discover the best time to fly to Guatemala from Newark with our price prediction graph.
Estimated round-trip price
Rates are based on past data. Find the cheapest month and day to book your flight based on your travel requirements, then search for cheap deals.

Cheapflights Insights

Everything you need to know about your flight from Newark Airport to Guatemala

What is the cheapest month to book a flight from Newark Airport to Guatemala?

Currently, October is the cheapest month in which you can book a flight from Newark Airport to Guatemala (average of $160). Flying from Newark Airport to Guatemala in December is currently the most expensive (average of $322). There are several factors that can impact the price of a flight, so comparing airlines, departure airports and flight times can provide users with more options.

What is the cheapest time of day to fly from EWR to GT?

Find hourly flight availability from Newark to Guatemala. Discover flight options and departure times throughout the day, allowing you to choose a departure time that suits your schedule. Data last updated October 17, 2025.

A simple way to save on the total cost of your ticket is to fly from Newark Airport to Guatemala in the evening. If you’re flexible enough to do this you can expect to save up to 30% on your trip compared to booking a flight in the afternoon.

What is the cheapest day to fly from Newark Airport to Guatemala?

Use this chart to determine the cheapest time to fly round-trip from Newark to Guatemala. Price data was last updated on December 16, 2024.

Travelers seeking maximum savings on their Newark Airport to Guatemala flight should consider departing on Thursday evenings when fares are most often at their lowest. Friday at noon flights should be avoided if possible as fares are typically the most expensive at this time.

Weekly flight availability from Newark Airport to Guatemala

Explore weekly flight availability from Newark to Guatemala. Discover flights operating on different days of the week, giving you the flexibility to choose a travel day that best fits your plans. Compare info to find the most convenient option for your journey. Data last updated October 17, 2025.

The most flights from EWR to GT0 are scheduled on a Monday (2 on average). You will have fewer flight options on Monday, which is when the least amount of flights are scheduled (2 on average).

Reviews of airlines servicing Guatemala

Get insights into the airlines that provide service to Guatemala. Read reviews, discover amenities, and learn about the overall travel experience offered by airlines. Use this information to make informed decisions when choosing an airline for your flight to Guatemala. Reviews last updated October 17, 2025.
Read through reviews of airlines operating flights from Newark Airport to Guatemala, such as United Airlines, American Airlines, and JetBlue. Reviews also offer insight into each airline's entertainment options, comfort, food, crew/service, and boarding process.
United Airlines
7.4
Good
8,987 reviews

Food

6.6

Crew

8.1

Comfort

7.3

Overall

7.4

Boarding

7.7

Entertainment

7.1

Reviews

1 / 20
4.0
Okay

Tim,Sep 2025

IAD - GSP

This was pretty bad. It’s chaos at the Dulles boarding gates for the small regional jets because they use one gate to board 3-4 flights at a time. So, it’s difficult knowing where and when to go. There is little space for any size of carrry-on, so most had to gate check their bags. However, the worst of it was that our single flight attendant fell asleep before we took off and the pilot couldn’t do so until she responded to his messages. My wife had to wake her up! So we were a little late leaving. Not to be thwarted, the flight attendant fell asleep right after take off and there was no sight of her during the flight. When the aircraft touched down, a tray of unsecured canned drinks came crashing onto the aisle up front. I can only assume someone didn’t do what they were supposed to. The pilot was great, but I’m sure he must not be happy with this crew member.
United Airlines
7.4
Good
8,987 reviews
United Airlines
7.4
Good
8,987 reviews

Food

6.6

Crew

8.1

Comfort

7.3

Overall

7.4

Boarding

7.7

Entertainment

7.1

Reviews

1 / 20
4.0
Okay

Tim,Sep 2025

IAD - GSP

This was pretty bad. It’s chaos at the Dulles boarding gates for the small regional jets because they use one gate to board 3-4 flights at a time. So, it’s difficult knowing where and when to go. There is little space for any size of carrry-on, so most had to gate check their bags. However, the worst of it was that our single flight attendant fell asleep before we took off and the pilot couldn’t do so until she responded to his messages. My wife had to wake her up! So we were a little late leaving. Not to be thwarted, the flight attendant fell asleep right after take off and there was no sight of her during the flight. When the aircraft touched down, a tray of unsecured canned drinks came crashing onto the aisle up front. I can only assume someone didn’t do what they were supposed to. The pilot was great, but I’m sure he must not be happy with this crew member.
American Airlines
7.2
Good
11,036 reviews
United Airlines
7.4
Good
8,987 reviews

Food

6.6

Crew

8.1

Comfort

7.3

Overall

7.4

Boarding

7.7

Entertainment

7.1

Reviews

1 / 20
4.0
Okay

Tim,Sep 2025

IAD - GSP

This was pretty bad. It’s chaos at the Dulles boarding gates for the small regional jets because they use one gate to board 3-4 flights at a time. So, it’s difficult knowing where and when to go. There is little space for any size of carrry-on, so most had to gate check their bags. However, the worst of it was that our single flight attendant fell asleep before we took off and the pilot couldn’t do so until she responded to his messages. My wife had to wake her up! So we were a little late leaving. Not to be thwarted, the flight attendant fell asleep right after take off and there was no sight of her during the flight. When the aircraft touched down, a tray of unsecured canned drinks came crashing onto the aisle up front. I can only assume someone didn’t do what they were supposed to. The pilot was great, but I’m sure he must not be happy with this crew member.
JetBlue
7.2
Good
2,907 reviews
United Airlines
7.4
Good
8,987 reviews

Food

6.6

Crew

8.1

Comfort

7.3

Overall

7.4

Boarding

7.7

Entertainment

7.1

Reviews

1 / 20
4.0
Okay

Tim,Sep 2025

IAD - GSP

This was pretty bad. It’s chaos at the Dulles boarding gates for the small regional jets because they use one gate to board 3-4 flights at a time. So, it’s difficult knowing where and when to go. There is little space for any size of carrry-on, so most had to gate check their bags. However, the worst of it was that our single flight attendant fell asleep before we took off and the pilot couldn’t do so until she responded to his messages. My wife had to wake her up! So we were a little late leaving. Not to be thwarted, the flight attendant fell asleep right after take off and there was no sight of her during the flight. When the aircraft touched down, a tray of unsecured canned drinks came crashing onto the aisle up front. I can only assume someone didn’t do what they were supposed to. The pilot was great, but I’m sure he must not be happy with this crew member.
Avianca
6.7
Okay
2,455 reviews
United Airlines
7.4
Good
8,987 reviews

Food

6.6

Crew

8.1

Comfort

7.3

Overall

7.4

Boarding

7.7

Entertainment

7.1

Reviews

1 / 20
4.0
Okay

Tim,Sep 2025

IAD - GSP

This was pretty bad. It’s chaos at the Dulles boarding gates for the small regional jets because they use one gate to board 3-4 flights at a time. So, it’s difficult knowing where and when to go. There is little space for any size of carrry-on, so most had to gate check their bags. However, the worst of it was that our single flight attendant fell asleep before we took off and the pilot couldn’t do so until she responded to his messages. My wife had to wake her up! So we were a little late leaving. Not to be thwarted, the flight attendant fell asleep right after take off and there was no sight of her during the flight. When the aircraft touched down, a tray of unsecured canned drinks came crashing onto the aisle up front. I can only assume someone didn’t do what they were supposed to. The pilot was great, but I’m sure he must not be happy with this crew member.
Spirit Airlines
6.3
Okay
8,102 reviews
United Airlines
7.4
Good
8,987 reviews

Food

6.6

Crew

8.1

Comfort

7.3

Overall

7.4

Boarding

7.7

Entertainment

7.1

Reviews

1 / 20
4.0
Okay

Tim,Sep 2025

IAD - GSP

This was pretty bad. It’s chaos at the Dulles boarding gates for the small regional jets because they use one gate to board 3-4 flights at a time. So, it’s difficult knowing where and when to go. There is little space for any size of carrry-on, so most had to gate check their bags. However, the worst of it was that our single flight attendant fell asleep before we took off and the pilot couldn’t do so until she responded to his messages. My wife had to wake her up! So we were a little late leaving. Not to be thwarted, the flight attendant fell asleep right after take off and there was no sight of her during the flight. When the aircraft touched down, a tray of unsecured canned drinks came crashing onto the aisle up front. I can only assume someone didn’t do what they were supposed to. The pilot was great, but I’m sure he must not be happy with this crew member.

Related info for your journey

Find useful and relevant information for your journey from Newark to Guatemala. Access travel guides, tips, and recommendations to enhance your travel experience. Get information about local attractions, weather, transportation options, and more.

  • How popular is this Newark Airport to Guatemala flight route?

    This flight path from Newark to Guatemala was viewed by 14 users in the past month. Keep an eye out for changes in search interest prior to high and low season.

  • How long is the flight from Newark Airport to Guatemala?

    United Airlines can get you from Newark Airport to Guatemala in just under 5h 14m. Your travel time will be generally consistent. Airlines will cover a distance of 2054 mi. Generally, flights for this route are nonstop.

  • What are the cheapest airlines to fly from Newark Airport to Guatemala one-way?

    One-way options have recently been found by users for as low as $101 on Spirit Airlines. Other airlines that offer cheap prices include JetBlue from $109 and United Airlines from $124 one-way.

  • What are the cheapest flights from Newark Airport to Guatemala?

    While on average a flight from Newark Airport to Guatemala is generally $298, our data shows the cheapest flight currently is $91. When looking at the most popular route, (Newark - Guatemala City La Aurora), you can expect to pay $177 for that flight.

  • Can I find deals for flights from Newark to Guatemala that include hotel bookings?

    Yes. In addition to deals on Newark to Guatemala flights, Cheapflights offers vacation packages that include both flights and hotel.

  • How can I find direct flights from Newark to Guatemala?

    After entering your origin and destination, apply the non-stop filter on the search result page to find direct flights from Newark to Guatemala.

  • Can I find deals for business class flights from Newark to Guatemala?

    Yes. Cheapflights offers flight deals from Newark to Guatemala by cabin class. In addition to browsing deals, you can also filter by cabin class on the search results page after making a search.

  • What is the cheapest month to book a flight from Newark Airport to Guatemala?

    Currently, October is the cheapest month in which you can book a flight from Newark Airport to Guatemala (average of $160). Flying from Newark Airport to Guatemala in December is currently the most expensive (average of $322). There are several factors that can impact the price of a flight, so comparing airlines, departure airports and flight times can provide users with more options.

See more FAQs

Browse thousands of different options on Cheapflights for your next trip

Toggle through the tabs below to find thousands of options on Cheapflights for your next trip.

Alternative routes for Newark to Guatemala

See prices for flight routes from nearby airports that may be better suited for you.
John F Kennedy Intl to San José flights
Newark to San José flights
John F Kennedy Intl to Panama City flights
John F Kennedy Intl to San Salvador flights
John F Kennedy Intl to Guatemala City flights
Newark to Panama City flights
Newark to Guatemala City flights
LaGuardia to San José flights
Newark to Liberia flights
John F Kennedy Intl to Liberia flights
LaGuardia to Liberia flights
LaGuardia to Panama City flights
LaGuardia to San Salvador flights
John F Kennedy Intl to San Pedro Sula flights
LaGuardia to Guatemala City flights
Newark to San Salvador flights
Newark to Philip S.W.Goldson flights
LaGuardia to Philip S.W.Goldson flights
John F Kennedy Intl to Philip S.W.Goldson flights
John F Kennedy Intl to Managua flights
LaGuardia to San Pedro Sula flights
Newark to Managua flights
Newark to San Pedro Sula flights
LaGuardia to Managua flights
Newark to Coxen Hole flights
John F Kennedy Intl to Coxen Hole flights
LaGuardia to Coxen Hole flights
Stewart to San José flights
Newark to David flights
John F Kennedy Intl to David flights
Stewart to San Pedro Sula flights
John F Kennedy Intl to Tegucigalpa flights
Stewart to Guatemala City flights
Newark to Flores flights
Newark to Tegucigalpa flights
John F Kennedy Intl to Flores flights
LaGuardia to Flores flights
Stewart to Panama City flights
LaGuardia to Tegucigalpa flights
Newark to San Pedro Town flights
John F Kennedy Intl to La Ceiba flights
John F Kennedy Intl to Placencia flights

Top 6 airlines flying from Newark to Guatemala

Discover the top 6 airlines that operate flights from Newark to Guatemala. Compare their services, reliability, and customer satisfaction ratings to choose the airline that best suits your travel preferences and needs. Over the last 7 days, Cheapflights users made 2,558,603 searches. Data last updated October 17, 2025.
AirlineCheapestAverageFlexibilityOn-time
AviancaCheapest$118Average$444FlexibilityNo cancel feeOn-time71%
JetBlueCheapest$188Average$395FlexibilityNo cancel feeOn-time62%
Spirit AirlinesCheapest$193Average$443FlexibilityNo cancel feeOn-time65%
United AirlinesCheapest$273Average$521FlexibilityNo cancel feeOn-time69%
American AirlinesCheapest$294Average$555FlexibilityNo cancel feeOn-time71%
DeltaCheapest$297Average$463FlexibilityNo cancel feeOn-timeN/A

100% Free

Cheapflights is completely free to use, so you can start saving the moment you arrive.

Book with Flexibility

Our users can plan ahead with confidence and find flights with no change fees

Travel Smart

Millions of people come to us for their flight needs every year. We help make travel planning easy by providing useful insights and data-driven graphs that can inform your decisions.
Site
Cookie settings©2025 Cheapflights