a new generation of passenger jets, which will mainly use hydrogen as fuel, are in the offing. The aircraft will be cheaper to run and cleaner, leaving little more than a trail of water vapour across the sky ( Flight International , Vol 151, No 4565).

The new aircraft, called cry oplanes, will have bulbous cabins and stubby wings and carry frozen hydrogen in large refrigerated tanks above their fuselages, making them among the oddest looking crafts to fly, according to spokespersons at Daimler-Benz, Germany, which is manufacturing the planes. Its range is expected to be more than 6,000 km per flight as hydrogen provides three times more energy than a similar amount of kerosene. A small executive jet cryoplane will be in service by ad 2005.

The project has been kept a secret until now because engineers feared they would not overcome the enormous engineering problems. Hydrogen is so light that it boils at -253