A lawsuit is seeking to force the nation’s airlines to make big changes in order to better accommodate travelers with disabilities.

The suit filed this month against the U.S. Department of Transportation accuses the agency of unlawfully delaying rules aimed at adding accessible restrooms to single-aisle airliners.

In 2016, Congress directed the Transportation Department to release rules on airplane restroom accessibility, among other issues, by July 15, 2017.

However, to date, the agency has not released a rule on lavatory wheelchair access on single-aisle aircraft and the issue was recently moved to the Transportation Department’s long-term agenda, according to the suit filed by the Democracy Forward Foundation on behalf of Paralyzed Veterans of America in the 10th U.S. Circuit Court of Appeals.

“Accessing a restroom on an airplane is something that most Americans take for granted,” said David Zurfluh, president of Paralyzed Veterans of America. “We simply want DOT to move forward with the rulemaking process as Congress required. We have waited long enough.”

The veterans group said that the Air Carrier Access Act bars airlines from discriminating against travelers with disabilities, but that the Transportation Department has skirted rulemaking on lavatory accessibility on single-aisle aircraft since at least 1990.

Without accessible restrooms on most domestic flights, individuals with disabilities are often left uncomfortable or forced to resort to dehydration and other measures in order to travel long distances, the group said. At present, accessible lavatories are only required on planes with more than one aisle.

The suit asks the court to compel the Transportation Department to take action.

For its part, the Transportation Department said it could not comment on pending litigation. But, a spokeswoman indicated that the issue of accessible lavatories on single-aisle aircraft is on the agency’s long-term agenda though there is no scheduled timeline for rulemaking.