Three U.S. aviation unions, representing about 50,000 pilots and industry professionals, have sent letters to Congress urging the adoption of the Republican budget bill to restore federal government funding, which has been temporarily halted since October 1, USA Today reports.

In their letters, the Coalition of Airline Pilots Associations, the National Federation of Federal Pilots, and the NetJets Pilots Association highlighted the difficult situation of 13,000 air traffic controllers nationwide, who have not been paid due to the shutdown, as well as challenges faced by employees of the Transportation Security Administration. The unions stressed that the lack of funding is worsening the sector’s problems and causing delays and disruptions at airports across the country. They urged Congress members to approve the bill being pushed by the Republican Party.

The current partial U.S. federal government shutdown began at midnight on October 1 due to a funding shortfall. The impasse arose because Republican and Democratic lawmakers in Congress could not reach agreement on several spending issues, including healthcare, and negotiations have not yet resolved the dispute. Both parties accuse each other of causing and prolonging the shutdown for political reasons.

Under U.S. law, departments responsible for national security and foreign policy must continue operating during a federal funding lapse. Similar requirements apply to employees whose work involves “protection of life and property.” Such employees work without pay during the shutdown but are usually compensated retroactively once funding is restored.