BSS/AFP) - Aviation groups urged US political leaders to quickly resolve a budget impasse Wednesday, warning that the government shutdown strains air travel and delays key upgrades.

The closure has led to staff furloughs throughout the government, even as vital functions such as aviation safety proceed.

Some 13,300 US air traffic controllers and thousands of other essential safety officials must work without pay, according to a Department of Transportation (DOT) operational plan.

The shutdown could delay key initiatives to recruit additional air traffic control staff and undertake a multi-billion modernization of the US air traffic control system, said the National Air Traffic Controllers Association.

"Congress must act now to end this shutdown," said NATCA President Nick Daniel.

"When the federal government shuts down it introduces unnecessary distractions and our entire aviation system is weakened. Congress must restore federal funding so that the safety and efficiency of our National Airspace System is not compromised."

NATCA said 2,350 aviation professionals in its membership have been furloughed, including aircraft certification engineers and aerospace engineers.

In all, the Federal Aviation Administration has furloughed more than 11,300 out of its 44,800 employees, according to the DOT shutdown plan.

It listed activities that will "cease" during the funding gap including aviation rulemaking, air traffic performance analysis, investment planning, and financial analysis and audit.

Airlines for America, which represents leading US carriers, urged congressional leaders to quickly remedy the situation.

"When federal employees who manage air traffic, inspect aircraft and secure our nation`s aviation system are furloughed or working without pay, the entire industry and millions of Americans feel the strain," the trade group said.

"We appreciate the men and women who will be going to work, despite not receiving a paycheck, to ensure the safety and security of the traveling and shipping public."