Now the rule is on notably shakier ground. Airlines for America, a trade association that represents the country’s biggest airlines, joined by member carriers American Airlines, JetBlue Airways, Southwest Airlines, United Airlines and Delta Air Lines, has filed a lawsuit in federal court arguing that the Transportation Department overstepped its statutory authority in adopting the measure.

The petitioners argued in an opening brief filed last week that the rule wrongly makes airlines liable for damaged wheelchairs even when they have not discriminated against disabled travelers, such as if mishandling was an “act of God” or beyond the airline’s control. One example they cited was if the wheelchair was in poor condition before the start of the trip. In those cases, they should not be held liable, they said, allowing that the rest of the rule’s provisions could be left in place. The lawsuit “simply seeks to ensure that D.O.T. acts within the scope of its authority to regulate only acts within airlines’ control and responsibility,” the brief reads.

A spokeswoman for Airlines for America said the group and its member airlines “are continuously engaged with the disability community, the Department of Transportation and others to identify and implement solutions to accessibility barriers.” The individual airlines who joined the suit said in statements to The New York Times that they were committed to accessibility and compliant with federal regulations, and most referred to the trade association’s comment on the petition.

The Transportation Department, meanwhile, has repeatedly delayed enforcing compliance with the rule, and has asked the court to pause the litigation while it reviews the rule to “ensure that it is consistent with the law,” according to a court filing. A department spokeswoman said its review would also cover administration policies and issues raised by the airlines’ lawsuit.

Advocacy groups and travelers who use wheelchairs said they’re alarmed by these developments, which they emphasized could have immediate consequences.