In light of today’s attacks in Belgium, several U.S.-based airlines are waiving their typical rebooking penalties and fees for travelers flying from, to, or through Brussels and several other European cities. 

U.S. airlines canceled or diverted several flights to and from Brussels’ Zavemtem Airport Tuesday following attacks that killed more than 30 people at the city’s airport and metro train stations.

USA Today reports that United Airlines has canceled four flights, Delta Air Lines two flights, and American one flight to the city, and all scheduled flights from the Brussels to the U.S.

While the cancellations cover immediate flights, the airlines are also allowing some passengers flying to, from, or through Brussels to reschedule upcoming trips free of charge.

Delta Air Lines says it will allow passengers who are booked on flights to or through Brussels, Amsterdam, or Paris between March 22 and March 31 a one-time flight change without incurring a fee.

Affected passengers must reschedule their flights by Sunday, March 27 and use the ticket by the end of the month, Delta says.

“When rescheduled travel occurs beyond March 31, 2016, the change fee will be waived. However, a difference in fare may apply,” the airline says. “Final travel must be completed by end of ticket validity, one year from date of original issue. If travel is not able to be rescheduled within these guidelines, customers may cancel their reservation and apply any unused value of the ticket toward the purchase of a new ticket for a period of one year from the original ticket issuance.”

Passengers on flights that have already been canceled will receive a full refund.

American Airlines is also waiving the fee for a one-time ticket change for passengers traveling to Brussels.

Eligible passengers must be flying on American Airlines, British Airways, or Iberia flights between March 22-23 to or through Brussels. Rescheduled flights can be set through April 6.

Passengers who choose not to change their ticket can receive a refund, the airline said.

Travelers on United Airlines’ flights to, from, or through Brussels can reschedule their March 22 and April 1 trips without a fee.

“Rescheduled travel departing after April 1, 2016, or for a change in departure or destination city, the change fee will be waived, but a difference in fare may apply,” United says. “Rescheduled travel must be completed within one year from the date when the ticket was issued.”

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