The U.S. Department of Transportation is easing some requirements it placed on airlines that received aid under a coronavirus spending bill, including mandates that they serve all airports they did before the lockdown, according to a notice issued Tuesday.

The roughly $2 trillion spending bill (PL 116-136) required airlines receiving aid to continue some level of service to the same airports they served before the pandemic all but shut down air travel.

At least 17 airlines, ranging from major players to small commuter lines, asked for exemptions from that requirement in the law (PL 116-136), forcing the DOT to weigh in on requests on hundreds of destinations, including many smaller airports or those near other large metropolitan airports.

Airlines often were compelled to send out nearly empty flights in order to meet those service obligations and have argued that maintaining the flights put them at further financial risk.

On Tuesday, the department said it would allow air carriers to create a prioritized list of destinations to stop serving. The DOT would have the right to refuse a request if it meant the affected airport would no longer receive any air service.

American Airlines and Delta, for example, were allowed to pick 11 airports where they could halt service, as long as another airline continues to provide flights to those destinations.

The DOT asked airlines to submit their list of exemption requests by 5 p.m. on May 18.

“The relief . . . will allow carriers to reduce their service obligations, thereby reducing carriers’ financial burden and providing flexibility to manage operations and staffing across their networks,” the DOT wrote in a statement announcing the new policy. It added that airports “will continue to receive service from at least one covered carrier.”

The DOT has a long history of requiring at least a minimum level of service to airports. The 1978 Airline Deregulation Act included a provision guaranteeing that small communities served by air carriers before deregulation continued to receive some level of service.

Joel Bacon, executive vice president of government and public affairs for the American Association of Airport Executives, said it makes little sense to fly nearly empty planes but that his organization is closely watching the rule.

“There are definitely concerns about maintaining viable air service options in the short term, but a recognition that airlines need to survive the immediate crisis in order to provide service into the future,” he said. “ Longer term, it’s clear that protecting air service and connectivity to the system will be a challenge that we’re all going to have to get our arms around.”

The department also Tuesday issued for the second time a notice urging airlines to give refunds for services changed or canceled because of the pandemic.

The three-page note reiterated that passengers who choose not to travel because of safety concerns are “generally not entitled to a refund or a travel voucher for future use on the airline.”

That guidance came after Sen. Richard Blumenthal, D-Conn., complained at a Senate Commerce, Science and Transportation hearing last week that airlines were not refunding tickets to passengers concerned about their health, and after the DOT received some 25,000 air travel service complaints and inquiries in March and April, compared to the 1,500 complaints it receives in a typical month.