Continental: As of today, Continental has extended its waiver to allow passengers to reschedule without penalty by the end of the month. Rescheduled flights to the same city will not require additional fare if booked in the same class. If your flight has been cancelled, you can request a refund. Or the value of your ticket also can go towards another flight. And passengers have a year from the issue date of the original reservation to complete their travel.
Delta: Will allow a one-time ticket change without any fare difference or change fees, provided your rescheduled flight is between the same city pairs and in the same class. If you want to change your destination, you will receive credit toward the purchase of a new ticket for a period of one year from the original issue date. No change fee will apply if you rebook by May 16. These options are for those traveling to/from/through Mexico April 26 to May 16.
United Airlines: No charge for first-time change to an itinerary. Accepting changes for those scheduled on flights through May 31. If you have not begun your trip, you will need to make changes within 21 days of the affected travel dates.
USAirways: Waiving change fee and advance ticketing requirements if you reschedule within 14 days of your original flight. Passengers can rebook for a new destination and apply the full value of wholly unused tickets toward the new ticket, however travel must originate within 14 days of the original scheduled date. (Yikes!) All other fare rules apply, which means you have to pay any difference in price between your old and new flights.
US3000: Waiving change fees if you reschedule your flight by 8 p.m. the day before scheduled departure. Passengers can rebook travel for any time before Dec. 15. Valid for passengers scheduled on flights April 25-May 13. You will need to pay any difference in fare.