The aerotower is a kind of aeroplane that consists solely of a long, flexible wing (ranging in length from 150 to 250 feet) from which are suspended various nacelles and propeller motors. Aerotowers are remotely controlled, using radio beams, powered by solar energy cells and usually carry scientific and photographic equipment. Invented by a Montreiano aircraft firm, the aerotower has seen almost exclusive use by the NAL-SLC and Australasia, both of which are using them for surface mapping, geological and meteorological studies. They have proven to be quite capable of flight above 90.000 feet and are also capable of staying aloft for long periods of time, up to six months. Several autonomous aeroplane types have been built over the years, but the aerotower has proven to be among the most stable of all the attempts. The Australasians are considering linking several aerotowers together in order to fly more equipment or perhaps people on long range scientific missions.