Wildfires are a serious problem every year across the western United States

Nearly 150 pilots and aircrew have been killed in the past 40 years, as well as many ground-based firefighters.

The Altus II unmanned plane is designed to act as a spotter rather than to do the seriously dangerous work of dropping water on the blazing forests.

But it is hoped that it will help firefighters stay out of danger and tackle the fires more effectively.

The plane is controlled by pilots on the ground through a video link, and can fly for 24 hours at up to 11 miles (about 18 kilometres) high.

It carries an infrared camera to pick out hot spots on the ground.

New-style satellites

The data is then sent to orbiting communication satellites which relay it to a receiving station on the ground.

It can then be sent on through the internet to fire crews in the front line.

This is another step in the rapid development of pilotless plane technology for both military and civilian use.

Only last month, the solar-powered flying wing Helios set a new altitude record for non-rocket-powered aircraft.

Industry scientists hope that in future unmanned craft may not only do much of the work of piloted planes more cheaply and safely, but even take over some of the functions of orbiting satellites.