WASHINGTON — NASA launched a program this month budgeted at more than $100 million aimed at allowing unmanned aircraft to share the skies with commercial airliners, bolstering what the defense industry hopes will eventually be a multibillion-dollar market for drones.

The program would initially permit unmanned aerial vehicles, known as UAVs, to fly at about 40,000 feet, which is above most commercial traffic. By the end of five years, unmanned aircraft would be allowed to join general air traffic, flying as low as 18,000 feet. At that altitude, the aircraft could monitor border areas or check for forest fires, industry officials said. The industry envisions drones eventually moving cargo across the country.

"The ability to enter national airspace is going to be a fundamental change to aviation," said Jeff Bauer, manager of the NASA project.

Under existing regulations, it takes up to two months to get Federal Aviation Administration permission to fly a drone in national airspace. That limits response to emerging situations such as floods or earthquakes, industry officials said. In many cases, the agency requires that a plane with a human pilot escort a drone, significantly increasing the cost of each trip, they said.

Recently, the FAA gave the Air Force more leeway in flying Northrop Grumman Corp.’s Global Hawk. The drone is now allowed to fly largely unfettered around the country as long as a flight plan is filed with the FAA five days in advance and the aircraft stays above 40,000 feet, company officials said.

But the concession covers only one drone and does not reach the level of freedom the industry envisions. Eventually, industry officials want to be able to file a flight plan in the same manner as any manned aircraft and take off from a commercial airport instead of an Air Force base.

NASA is funding the bulk of the cost, $100 million, and developing the program in conjunction with the Defense Department and the FAA. The defense industry, including the Boeing Co., Lockheed Martin Corp. and Northrop Grumman Corp., is expected to contribute an additional $30 million to $40 million. The program will develop technology, simulation tests and policies governing the planes’ use of the national airspace.

Government and industry officials have attempted for years to gain wider acceptance of unmanned planes but have been stymied by concerns that drones are not reliable enough to fly over populated areas. Some point to their spotty record in combat. During the Kosovo war, 10 times as many drones were lost as manned vehicles, according to a report from Teal Group Corp., a defense research firm.

Drones range in size from as large as a 747 to an aircraft with a 9-foot wingspan weighing just 10 pounds. Pilots on the ground operate the aircraft. Critics say that if a pilot loses contact, the unmanned aircraft could crash into a populated area.

Drones should be required to meet the same safety standards as commercial airliners, including enhanced crash-avoidance software, said John Mazor, spokesman for the Air Line Pilots Association, adding that NASA has not provided any details of the program. "There will be an awful lot of concerns that have to be satisfied" before drones can go into widespread use, Mazor said.

The program will spend a lot of its money developing technology to enhance a drone’s ability to detect another aircraft and avoid it, said Bauer, the NASA project manager. During the early phase of the program, the drones will be able to detect signals sent from commercial jet transponders so the pilot on the ground can avoid nearby traffic, according to industry officials.

The use of drones in domestic airspace could also raise privacy concerns, especially if the aircraft are adapted for public surveillance, said Barry Steinhardt, director of the Program on Technology and Liberty at the American Civil Liberties Union.

"The technological reality is that the government has the equivalent of Superman’s X-ray vision, and these unmanned planes are an example of that," he said. "Do we want to live in a society where drone planes … are constantly monitoring our every activity? That’s the question we’re going to have to answer."