A lawsuit filed against Southwest Airlines alleges the carrier violated its contract with customers by failing to provide refunds for flights canceled during the coronavirus pandemic.

In the suit, traveler Adrian Bombin says that when Southwest canceled his trip from Baltimore-Washington International Marshall Airport, via Florida, to Havana last month, he asked for a refund.

And, as has happened to many other travelers, Bombin said in the federal lawsuit filed Monday in Pennsylvania, the airline would offer him only a voucher.

The suit points to language in Southwest’s contract with customers, which says the airline in such situations would put customers on the next available flight or refund their fares “in accordance with the form of payment utilized for the Ticket.” It alleges Southwest violated that contract for Bombin and seeks class-action status to represent everyone Southwest has failed to refund since March 1.

“We’re not trying to ask them to do anything special because of covid. We’re only asking them to honor the agreement they wrote,” said Bombin’s attorney, Hassan A. Zavareei.

Other airlines, including United and Spirit, have also recently been sued under similar circumstances.

Southwest said in a statement that it offers “customer-friendly policies” and that people “may request a refund to the original form of payment.”

“Southwest will review this complaint and will defend our policies accordingly as our focus is always on taking care of our Customers, especially during these unprecedented times,” the airline said.

United said in a statement that “eligible travelers on both domestic and international flights” can request a refund “if their flights have been severely adjusted or service to their destination suspended either due to government mandates or United schedule reductions related to COVID-19.”

The airline said at one point it was providing credits to customers, but is now “providing refunds as outlined above and people who were provided credits can request for those to be converted into refunds.”

The Transportation Department said earlier this month that it has been receiving “an increasing number of complaints” from passengers being denied refunds, despite airlines’ “long-standing obligation” to provide them when they cancel flights or make significant changes to schedules.

“The focus is not on whether the flight disruptions are within or outside the carrier’s control, but rather on the fact that the cancellation is through no fault of the passenger,” the department said.

In a statement Tuesday, the department said it will monitor airlines’ refund practices and may issue warning letters or fines “as necessary.” But for now, it said, it is using its discretion “to give airlines an opportunity to come into compliance.”

A group of nine senators sent letters to airlines March 31 saying the “ongoing pandemic is placing enormous financial strain on millions of Americans, and families need cash to pay for essentials such as food, housing, and medical care.

“In light of this pressing need and the unprecedented bailout — to the tune of $25 billion — that the airline industry just received from Congress, we believe your company has a moral responsibility to provide real refunds, not travel vouchers, to consumers,” the letter read.