WASHINGTON — The US Senate on Monday adopted a bill to fund the Federal Aviation Administration (FAA), sending it to President Barack Obama despite a provision angrily opposed by Democrats' labor-union allies.

The Democratic-led chamber voted 75-20 to approve the measure, which had cleared the Republican-held House on Friday by a 248-169 margin.

The legislation, fruit of a compromise between the polarized US Congress's Republican and Democratic leaders, would provide the FAA $15.9 billion per year through fiscal year 2015 after years of temporary extensions in funding.

Organized labor, which Democrats hope will provide vital fundraising and organizational support in the November elections, fiercely objected to a provision that makes it harder for airline or railroad employees to form a union.

"Airline and rail workers would suffer significant losses as contracts are jettisoned, collective bargaining rights are cut and legal hurdles will be placed in the way of gaining a voice at work," 19 unions said in a joint statement when the legislation was announced January 30.

Democratic backers of the compromise bill said the House version would have cut more deeply into labor union organizing.

The FAA has been a political battleground over the past five years, funded with stopgap measures and hit with a shutdown last summer when one measure lapsed without a replacement in the works.

The legislation includes subsidies for rural airports, some of them in the home states of powerful Democratic lawmakers, and calls for upgrading air-traffic control technology.