A specially adapted aircraft has become the first to fly "unmanned" across shared British airspace as part of an experiment, researchers said.

While an on-board pilot handled the takeoff and landing for the 500-mile flight, during the journey the aircraft was controlled by a pilot on the ground, instructed by the National Air Traffic Services, the BBC reported Monday.

There were no passengers aboard, but the 16-seater aircraft flew in airspace shared with commercial airline flights, using its on-board sensors and robotics to identify and avoid hazards, the researchers said.

National Air Traffic Services "ensured that this test flight was held without any impact on the safety of other users of airspace at the time," service spokesman Andrew Chapman said.

The test flight of the Jetstream aircraft was part of a program dubbed Astraea, which has received $95 million from commercial companies and the British government to research how civilian unmanned aircraft could fit in to shared airspace.

"Astraea has made significant achievements, placing the United Kingdom industry in a good position globally on unmanned aircraft and the development of regulations for their civil use," Britain's Business and Energy Minister Michael Fallon said.

Getting unmanned aircraft into shared airspace was more than just a technical challenge, Astraea project manager Lambert Doppin-Hepenstal said when the project was announced last year.

"It's not just the technology; we're trying to think about the social impact of this and the ethical and legal things associated with it," he said.

"You've got to solve all this lot if you're going to make it happen, enable it to happen affordably."