Security screening lines are so long at some U.S. airports that major airlines are letting passengers cancel or rebook their tickets free of charge during the ongoing partial federal government shutdown. 

Travelers face hours-long wait times at TSA checkpoints, while others struggle to determine how early they should show up before a flight, given seemingly conflicting information from airports and airlines. TSA officers are also quitting in droves as they work without pay for a sixth straight week, with lawmakers still unable to pass a spending bill to fund the Department of Homeland Security, which oversees TSA.

Amid the chaos, airlines including Allegiant Air, Delta Air Lines and United Airlines are temporarily waiving cancellation and change fees in some instances.  Here’s what to know.

Allegiant

Allegiant has issued a “travel with confidence” guarantee that lets customers traveling during the partial government shutdown “change or cancel their itineraries at no additional cost, making it easier to plan trips with confidence.”

For a limited time, the carrier is offering fliers no change fees for eligible bookings, plus the option to cancel a flight for a refund. Customers must contact Allegiant’s customer service team directly by phone, chat, text or email to change or cancel a flight. 

At the same time, the airline is encouraging passengers who choose to travel to allow for extra time at airport security screening lines. It urges customers to check either their local airport’s website or social media channels for projected TSA wait times. 

Delta

Delta’s waiver specifically applies to Hartsfield-Jackson Atlanta International Airport, which advises flight passengers to allow at least four hours for domestic and international flight security screening.  

Passengers with plans to travel on Tuesday may rebook their trips to fly on or before March 30, according to Delta. The carrier said it will waive any fare differences in flights for passengers who book tickets in the same cabin of service they originally selected. 

United

United Airlines, which notes that it has already eliminated most ticket change fees, has issued a special waiver for travelers flying to or from George Bush Intercontinental Airport in Houston, where passengers have faced wait times of up to six hours due to TSA worker absences. 

United passengers with original travel dates on March 23-24 may reschedule trips, with the airline saying it will waive all change fees and fare differences. Some conditions apply — the new flight must depart on or before March 31, and tickets must be in the same cabin and between the same cities as originally booked.