Delta Air Lines rounds out the list of the five carriers studied when it comes to cheap last-minute flights. With an average last-minute ticket price of $369.12, travelers would be wise to look elsewhere when looking to book shortly before departure.

American Airlines comfortably edges out rival Delta with an average last-minute flight cost of $282.61 and is the best airline to book for a last-minute cross-country flight as travelers can book a flight from John F. Kennedy International in New York City to Los Angeles International Airport for as low as $366.60.

United Airlines costs $272.80 for a last-minute ticket on average, the study found. Nonetheless, customers flying between L.A. and San Francisco or New York City and Chicago can really protect their budget while still booking late as United can fly them from SoCal to Silicon Valley for as little as $146.78 and from the Big Apple (LaGuardia Airport) to the Windy City (O'Hare) from as low as $189.56.

Low-cost carrier Southwest Airlines is one of the most wallet-friendly options for travelers booking last-minute flights, boasting an average ticket price of $233.72. Upgraded Points found that Southwest is the best option for the most affordable last-minute flight from L.A. to Maui (Kahului Airport) at a very affordable $174.50.

Ultra-low-cost carrier Spirit Airlines currently offers the most affordable last-minute flights, with an average price of $170.09 across the 10 routes analyzed. Some flights are even cheaper, however, as Spirit customers can fly Denver to Las Vegas for under $90 or Atlanta to Fort Lauderdale for less than $109.