Leaving on a Friday is a viable option for saving on travel. Heavily demanded days of the week can typically drive up the prices you see. Booking your travel for a less competitive day can save up to 64% on the overall cost on flights from St Louis to Bilbao.
Flights from St Louis to Bilbao lean towards being more expensive in April. Prices are generally better when you fly from St Louis to Bilbao in February, with the cheapest ticket starting at $548.