Under orders to trim hundreds of millions of dollars from its budget, the Federal Aviation Administration released a final list Friday of 149 air traffic control facilities that it will close at small airports around the country starting early next month.

The closures will not force the shutdown of any of those airports, but pilots will be left to coordinate takeoffs and landings among themselves over a shared radio frequency with no help from ground controllers. All pilots are trained to fly using those procedures.

The plan has raised concerns since a preliminary list of facilities was released a month ago. Those worries include the impact on safety and the potential financial effect on communities that rely on airports to help attract businesses and tourists.

“We will work with the airports and the operators to ensure the procedures are in place to maintain the high level of safety at nontowered airports,” FAA Administrator Michael Huerta said in a statement.

The FAA is being forced to trim $637 million for the rest of the fiscal year that ends Sept. 30. The agency said it had no choice but to subject most of its 47,000 employees, including tower controllers, to periodic furloughs and to close air traffic facilities at small airports with lighter traffic. The changes are part of the across-the-board spending cuts known as sequestration, which went into effect March 1.

All of the airports targeted for tower shutdowns have fewer than 150,000 total flight operations per year. Of those, fewer than 10,000 are commercial flights by passenger airlines.

Airport directors, pilots and others in the aviation sector have argued that stripping away an extra layer of safety during the most critical stages of flight will elevate risks and at the very least slow years of progress that made the U.S. aviation network the safest in the world.

Airlines have yet to say whether they will continue offering service to airports that lose tower staff. Any scaling back of passenger service could have major economic impact for communities.

The 149 air traffic facilities slated to begin closing April 7 are all staffed by contract employees who are not FAA staffers. There were 65 other facilities staffed by FAA employees on the preliminary list of towers that could be closed. A final decision on their closure will require further review, the FAA said.

The agency is also considering eliminating overnight shifts at 72 facilities, including some at major airports like Chicago’s Midway International and General Mitchell Airport in Milwaukee. There was no word Friday on when a decision will come.