WASHINGTON — A bill to speed the nation’s switch from radar to an air traffic control system based on GPS technology, and to open U.S. skies to unmanned drone flights within four years, received final congressional approval Monday.

The bill passed the Senate 75-20, despite labor opposition to a deal cut between the Democratic-controlled Senate and the Republican-controlled House on rules governing union organizing elections at airlines and railroads. The House had passed the bill last week, and it now goes to President Obama for his signature.

Republican Sens. Susan Collins and Olympia Snowe of Maine voted for the bill. Snowe noted that the final deal kept in place a federal program subsidizing commercial service at rural airports, including four in Maine: Augusta, Rockland, Bar Harbor and Presque Isle.

“After 23 short-term extensions, it is long past time to reauthorize the FAA’s critical programs, like the Essential Air Service, which ensures safe, reliable and cost-effective air travel for passengers across rural Maine,” Snowe said in a written statement.

The bill authorizes $63.4 billion for the Federal Aviation Administration over four years, including about $11 billion toward the air traffic system and its modernization. It accelerates the modernization program by setting a deadline of June 2015 for the FAA to develop new arrival procedures at the nation’s 35 busiest airports so planes can land using the more-precise GPS navigation.

Instead of time-consuming, fuel-burning, stair-step descents, planes will be able to glide in more steeply with their engines idling. Planes will also be able to land and take off closer together and more frequently, even in poor weather, because pilots will know the precise location of other aircraft and obstacles on the ground. Fewer planes will be diverted.

Eventually, FAA officials want the airline industry and other aircraft operators to install onboard satellite technology that updates the location of planes every second instead of radar’s every six to 12 seconds. That would enable pilots to tell not only the location of their plane, but other planes equipped with the new technology as well – something they can’t do now.

The system is central to the FAA’s plans for accommodating a forecasted 50 percent growth in air traffic over the next decade.

The bill is “the best news that the airline industry ever had,” said Sen. Jay Rockefeller, D-W.Va. “It will take us into a new era.”

The FAA is also required under the bill to provide military, commercial and privately owned drones with expanded access to U.S. airspace currently reserved for manned aircraft by Sept. 30, 2015. That means permitting unmanned drones controlled by remote operators on the ground to fly in the same airspace as airliners, cargo planes, business jets and private aircraft.

– MaineToday Media Washington Bureau Chief Jonathan Riskind contributed to this report.