To save on the cost of your flight from St. Louis to Portsmouth, New Hampshire, book at least 54 days before your planned departure. Booking around this time can save you about 37% on the cost of this flight compared to booking a flight leaving this week. We have found prices from $250 if you need a flight within two weeks. For flights within the next 72 hours, you can find tickets from as low as $307.
When flying from St. Louis to Portsmouth, New Hampshire, the time of day you decide to fly out makes little to no difference towards the overall price you’ll pay on tickets.