The Department of Transportation’s website, Transportation.gov, provides a resource it calls, Fly Rights, that includes a wide array of information about air travel in the U.S. 

If a business traveler’s plans change, what are the rules about changing airline tickets?

Federal rules require U.S. and international airlines with flights in the U.S. to do one of the following:

1 | Give travelers 24 hours to cancel a ticket purchased at least seven days before departure

 2 | Hold a reservation at the quoted fare for 24 hours, after which it disappears unless you confirm and pay.

Most major U.S. and international airlines go with the first option: They allow travelers to cancel a ticket booked directly through the airline, without penalty, within 24 hours of purchase.

Beyond that, there are no rules that require an airline to change your flight. However, all airlines want your business and will work with you in several ways. If you are a participant in a frequent flier program, the airline will be especially accommodating.

Note | Booking sites like Expedia and Priceline, do not have to comply with the federal rule, but most offer a similar window for canceling some kinds of tickets.

Discount fares typically are non-refundable

While many national and international airlines will refund your ticket up to seven days before your scheduled flight, most discount fares are non-refundable. They typically opt for option #2 above and will hold a reservation, without pay, for the first 24 hours. After you purchase your ticket, they may not refund your payment, but will allow you to apply your ticket’s value to another trip in the future — but there may be a steep fee.  Many fares also have a penalty for changing flights or dates even if you don’t want a refund. You may also have to pay any difference in air fares if your fare type is not available on the new flight.

(via: Kiplinger.com)