The global software outage last week caused thousands of travelers flying in the United States and internationally to have their flights delayed, canceled or both. In the days that followed, some airlines were trying to reboot critical computer systems affected by the outage, with many of their passengers still stranded at airports.

During a travel meltdown, it may seem nearly impossible for air travelers to find immediate help. Gate agents are swamped, customer service phone lines have hourslong hold times, and seemingly confusing or incomplete instructions online only add to the headaches.

Passengers who foot the bill for last-minute lodging and other expenses are entitled to reimbursement if their flights were impacted by an event in the airlines’ control, like the CrowdStrike outage. Here’s how to get your money back.

If they caused the disruption, airlines owe passengers assistance.

It is the airline’s fault when a situation under their control — issues with crew, maintenance, baggage and fuel, or software outages — leads to a delay or cancellation. Weather and air traffic control issues do not count. On Friday, the Transportation Department noted that this IT outage fell under the control of the airlines.

What passengers will get from airlines depends on how long they were forced to wait, but it could include transport to and from hotels and the costs of accommodation.

Know what you are owed, and ask for it.

Strategize your ask. Gate agents may not always know the airline’s commitments or the Transportation Department policies. Usually, airlines prefer to take care of the details, distributing vouchers or directly booking hotel rooms. But during the CrowdStrike fallout, they initially did not believe they were required to provide assistance and later, seemingly, remained unaware of their obligations in some instances or were too overwhelmed by the numbers.

That meant many travelers had to take matters into their own hands to find transport, accommodation and meals, but they are eligible for reimbursement. However, how much will vary by airline and travelers won’t necessarily know before submitting receipts.

Reimbursement can generally be requested through an online form — hold onto your receipts!

Some airlines have online forms for reimbursement requests, while others will require you to contact customer service to start the process.

If your flight was canceled and you decided not to rebook, you can get a refund.

Don’t expect this to be seamless or automatic. Airlines generally have online forms where you can request refunds; you’ll need all of your trip details for this. You can get a refund to your original form of payment; you do not need to accept flight credits or a travel voucher. In addition, you can contact the airline’s customer service team for more help and to check on the status of your claim.

Check the fine print of your credit card agreement or travel insurance policy.

If you purchased travel insurance, the policy could cover certain types of trip interruptions, including select air travel issues — and your credit card agreement might also, though it may have a requirement that the affected flight was booked using it.

Here, too, remember to save your receipts and any other documentation, and brace yourself for a possibly lengthy process.

Consider lodging a complaint with the Transportation Department.

Today, Transportation Secretary Pete Buttigieg said the agency had opened an investigation into Delta’s response to the outage, after receiving numerous passenger complaints about the carrier. If you have a complaint yourself, you can submit it at https://secure.dot.gov/air-travel-complaint.

That form can be used for concerns or comments related to other airlines as well, but not for security or safety issues. The Transportation Department investigates complaints, though they advise passengers to contact airlines first.

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This article originally appeared in The New York Times.