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 Barack Obama for his signature.

The bill authorizes US$63.4 billion for the Federal Aviation Administration over four years, including about US$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 forecast 50 percent growth in air traffic over the next decade. Most other nations already have adopted satellite-based technology for guiding planes, or are heading in that direction, but the FAA has moved cautiously. The U.S. accounts for 35 percent of global commercial air traffic and has the world's most complicated airspace, with greater and more varied private aviation than other countries.

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

Transportation Secretary Ray LaHood said the bill "will provide the stability and predictability to ensure critical aviation safety programs ... and infrastructure investments move forward."

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 Sep. 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.

Currently, the FAA restricts drone use primarily to segregated blocks of military airspace, border patrols and about 300 public agencies and their private partners. Those public agencies are mainly restricted to flying small unmanned aircraft at low altitudes away from airports and urban centers.

Within nine months of the bill's passage, the FAA is required to submit a plan on how to safely provide drones with expanded access.

The bill's passage culminates a five-year struggle by Congress to pass a long-term FAA authorization bill. The last long-term operating authorization for the agency expired in 2007. The agency has continued to limp along under a series of 23 short-term extensions, but its ability to commit to decisions on major acquisition programs that extend over many years, like air traffic modernization, was hindered by the uncertainty over how much it could spend and by a lack of direction from Congress.

Providing that stability is critical to the health of the commercial aviation industry, which accounts for about 5 percent of U.S. economic output, lawmakers said.

Several labor issues over the years have frustrated efforts to pass a bill. Most recently, a Republican-drafted bill that cleared the House last spring included a provision that would have overturned a National Mediation Board ruling allowing airline and railroad employees to form a union by a simple majority of those voting. Under the old rule, workers who didn't vote were treated as "no" votes.

The labor provision, which was opposed by the Democratic-controlled Senate, became the principal issue holding up the bill. A compromise reached two weeks ago by Senate Majority Leader Harry Reid, D-Nev., and House Speaker John Boehner, R-Ohio, allows the mediation board's rules to stand, but it also toughens some lesser requirements that must be met in order to hold a union organizing election.

While the compromise was acceptable to some unions, more than a dozen other unions that represent airline industry workers -- including the Teamsters, Communications Workers, Machinists and Flight Attendants -- complained the deal was reached without their input and urged its rejection.

Sen. Tom Harkin, D-Iowa, said he decided to vote against the bill because of the labor provisions even though the measure contains "many good things." He said he was taking a stand against "a few of these powerful companies who don't want their workers to have representation" because someday they "might have to put a few additional dollars in their workers' pockets."

The bill also limits air service subsidies to the approximately 150 communities that already receive subsidized service. And it would trim about a dozen communities from the program after a year if they are within 175 miles of a hub airport and average less than 10 passengers a day, at a savings of about US$20 million a year.

House Republicans initially had proposed eliminating the entire US$200 million-a-year program except for subsidized service in Alaska and Hawaii. Conservatives had singled out the program as an example of government extravagance.

Last summer, a partisan standoff over a House attempt to cut 13 cities from the program, as well as the labor provision, resulted in two-week, partial shutdown of the FAA. More than 4,000 FAA employees were furloughed, work was halted on more than 100 airport construction projects and the government lost an estimated US$350 million in airline ticket taxes.