With more than 300 daily departures to 66 cities in the United States and eight international destinations, BWI Thurgood Marshall Airport is ranked among the top 25 busiest airports in the United States. For an airport with so many options, it would seem that it would be easy to find reasonably priced flights to a variety of locations. Yet, even the savviest traveler can fall victim to the strategies employed by airlines to ensure that customers pay as much as possible to reach their destinations.

If you are looking to join the crowds flying out of BWI Marshall this year, travel smart. You can do so by heeding these three tips to outsmart the airlines.

Tip No. 1: Take advantage of Southwest’s lack of change fees.

Have you ever booked your flight only to find out that the airline decreased its price the next day? Most airlines will charge a fee, ranging from $75 (American Airlines) to $150 (Delta Air Lines), to re-book a flight at a lower price. Southwest does not charge a fee, so whenever traveling Southwest, book early and periodically check the web site for a lower price. If the ticket was paid with a credit card, Southwest provides the price difference as a credit towards future travel within the next year; however, make sure you know your confirmation number when booking your next flight.

Even better, Southwest directly credits your account if you paid using Southwest’s Rapid Rewards points. If you’re not flying with Southwest, you can sign up for Tripit Pro, which will inform you of lower fares and provides other services.

Tip No. 2: Book your flight after you get home from work.

Have you ever looked up a price one night and found that it unexpectedly jumped the next day? A recent paper by economists Diego Escobari, Nicholas Rupp and Joseph Meskey finds that airlines tend to charge higher prices during normal business hours.

Airlines assume that people going to their web site during the day are booking business travel and are not concerned about prices. You should wait until the evening to book your family vacation. Do not book too late, though, as airlines tend to increase their airfares around 3 a.m., while most people are sleeping and unaware of these price changes.

Tip No. 3: Best day to book travel: Sunday

Many frequent fliers know that airports are busiest on Fridays and Mondays, but did you know that the best day to buy your ticket is typically on a Sunday? According to a recent Wall Street Journal article by Scott McCartney, airlines tend to start the workweek with an increase in price, not a sale. Also, travelers are less likely to book business travel during the weekend, which leads to lower prices.

With the expansion of Southwest’s route network into international destinations and the recent entry by Alaska Airlines, the variety of vacation destinations out of BWI Marshall are plentiful and growing. To save a few dollars, book your flights on the weekend or weekday evenings — and don’t forget to periodically check for lower prices if flying with Southwest.

Kerry Tan is an assistant professor of economics at Loyola’s Sellinger School of Business, which has a campus in Columbia. He can be reached at 410-617-2460 and kmtan@loyola.edu.