Airline passengers stranded by Friday's nationwide ground stop have several options to change their travel plans without paying additional fees, and federal regulations may entitle some travelers to a full cash refund. The FAA lifted the four-hour ground stop just after 8 p.m. ET, but airlines warned that heavy delays and residual cancellations would stretch into the weekend. Travel experts urged fliers not to cancel their reservations themselves while a flight is still listed as delayed, since canceling voluntarily before the airline officially cancels could leave customers with a travel credit instead of a cash refund they might otherwise qualify for under Department of Transportation rules.

Delta Air Lines expanded its fee-free rebooking window through Nov. 21, after an initial waiver covering flights scheduled for Nov. 13 and 14. Under the expanded window, affected passengers can change their travel plans without change fees, and without fare differences if they remain in their original cabin and booking class. United Airlines is waiving both change fees and fare differences for replacement flights departing between Nov. 12 and Nov. 20, provided new bookings stay in the same cabin and between the same cities, and passengers who no longer want to travel can cancel for a full refund. American Airlines is waiving change fees for all fare classes, including Basic Economy, for tickets purchased by Nov. 12 for travel on Nov. 13 or 14, with rebooked flights departing between Nov. 13 and Nov. 17 on the same routes; fare differences may still apply.S1

Southwest Airlines is allowing affected passengers to rebook without change fees within five days of their original travel date. Frontier Airlines is offering fee-free flight changes for travel scheduled between Nov. 13 and 15, and Alaska Airlines is allowing travelers to change or cancel without change fees or fare differences. JetBlue is waiving change and cancellation fees, as well as fare differences, for passengers scheduled to fly on Friday whose tickets were purchased before that day, with rebooking available online for travel through Wednesday, Nov. 18. United and JetBlue also announced cancellations affecting the vast majority of their remaining Friday night flights, with select international routes among the exceptions.S1