Delta Air Lines has offered its most substantial assistance to passengers yet following the IT outage that canceled thousands of flights last week.

On Wednesday, the airline announced it will reimburse travelers who booked a flight on a different airline amid the chaos of last week’s CrowdStrike meltdown. The airline had already promised to reimburse travelers for rental car or hotel expenses, but previously stopped short of paying for another airline fare.

“We know many customers have incurred unplanned travel expenses, including purchasing tickets on other airlines, rental cars, train tickets and more,” the airline said in its latest update. “Delta will cover reasonable costs for additional categories of expenses incurred during the duration of the travel waiver.”

Although the airline didn’t disclose what “reasonable” expenses are, they directed passengers to submit a request though a refund page on their website.

Delta will also extend its rebooking window and travel waiver through August 4. This means that if a traveler had a ticket booked between July 19 through July 28, they will have the ability to make a one-time change to the itinerary and the fare difference will be waived if it is in the same cabin of service originally booked. 

“To our customers who were impacted, I want to thank you for your patience and apologize again for the disruption to your travel,” Delta CEO Ed Bastian wrote in a published letter to customers. Bastian also noted that the airline has “made good progress” in stabilizing operations and that Thursday is expected to be “a normal day.”

The United States Department of Transportation (DOT) has published reminders to passengers of their rights through the FlightRights.gov website, and the opportunity to file a complaint. Passengers are encouraged to first contact their airline to resolve the issue promptly, before filing a complaint. 

“Before you contact DOT for help with an air travel problem, you should give the airline a chance to resolve it,” the DOT shares on the complaint site. “Airlines have trouble-shooters at the airports, usually called Customer Service Representatives, who can take care of many problems on the spot.”

If the airline is unable to process the refund or adjust the booking, travelers can file a complaint on the Department of Transportation website.