Washington (CNN) -- Thousands of employees have been furloughed and dozens of major projects put on hold after Congress failed to reauthorize funding for the Federal Aviation Administration, the agency said Monday.
Air traffic controllers will remain on the job, but the furloughs have hit many engineers, scientists, computer specialists, community planners and others. Nearly 4,000 employees in 35 states, Washington and Puerto Rico have been told to stop work, according to the FAA.
Efforts to continue funding hit a stumbling block over House Republican efforts to make it harder for airline and rail workers to unionize and over a move to cut subsidies for air service to rural airports.
Congress adjourned Friday without passing legislation, causing funding to end at midnight that night.
"Construction workers across America will lose their jobs and local communities will be hurt the longer this goes on. Congress needs to pass an FAA bill to prevent further economic damage," said Transportation Secretary Ray LaHood.
The FAA said contractors have been told to stop work on dozens of projects across the country, including a $43 million project in Las Vegas and a $31 million project in Oakland, California, to build air traffic control towers.
Without new legislation, the government will also not be able to collect about $200 million a week in airline taxes that normally go to the Airport and Airway Trust Fund. A $2.5 billion program providing grants for airport construction projects was similarly forced to shut down.
U.S. Sens. Barbara Mikulski and Ben Cardin, both Maryland Democrats, called on Congress last week to act before the then-imminent shutdown. Transportation officials said Congress had extended the FAA's funding almost 20 times without controversy.
"This shutdown will be unprecedented, and it will severely harm our economy and everyone who depends on a thriving aviation system. It also is a clear attack on federal employees who manage our nation's aviation and could have serious safety implications for air travelers," Cardin said last week.