WASHINGTON (AP) — The Senate has passed a compromise bill that speeds up the Federal Aviation Administration's switch from old-fashioned radar to an air traffic control system based on GPS technology. It also requires opening U.S. skies to drone flights within four years.

The bill was approved 75 to 20 on Monday 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 passed the bill last week. It now goes to President Barack Obama for his signature.

The bill authorizes $63 billion for the FAA over four years, including about $11 billion toward the air traffic system and its modernization.

The FAA is also required to give drones expanded access to U.S. airspace by September 2015.