Are unmanned aircraft, known to have difficulty avoiding collisions, safe to use in America's crowded airspace? And would their widespread use for surveillance result in unconstitutional invasions of privacy? Experts say neither question has been answered satisfactorily. Yet the federal government is rushing to open America's skies to tens of thousands of the drones - pushed to do so by a law championed by manufacturers of the unmanned aircraft. The 60-member House of Representatives' drone caucus" - officially, the House Unmanned Systems Caucus - has helped push that agenda. And over the last four years, caucus members have drawn nearly $8 million in drone-related campaign contributions. Domestic use of drones began with limited aerial patrols of the nation's borders by Customs and Border Patrol authorities. But the industry and its allies pushed for more, leading to provisions in the FAA Modernization and Reform Act, signed into law on Feb. 14 of this year. The law requires the FAA to fully integrate the unmanned aerial vehicles into national airspace by September 2015. The FAA has predicted that 30,000 drones could be flying in the United States in less than 20 years. House members from California, Texas, Virginia and New York on the bipartisan "drone caucus" received the lion's share of the funds channeled to lawmakers from dozens of firms that are members of the Association for Unmanned Vehicle Systems International.