An airship-type vehicle billed by its makers as the world’s longest aircraft currently in operation has been unveiled in Britain.

The Airlander, which was originally developed for the US military, is 300 feet (91m) long, according its British maker Hybrid Air Vehicles.

The environmentally friendly helium-filled behemoth is designed to stay airborne for up to three weeks and can carry up to 60 tonnes, the company said.

It was shown off on Friday in a giant hangar in Cardington, central England, where great British airships of the past were built, including the ill-fated R101.

The R101 crashed in 1930 on its maiden voyage, killing 48 passenger and crew.

The new craft is longer than the current record holder, the Russian Antonov An-225, which is 84 metres long, and the Boeing 747-8, at 76 metres long.

But it is dwarfed by airships of the past such as the German zeppelin the Hindenburg, which was 244 metres long.

Filled with hydrogen, the Hindenburg famously crashed in the United States in 1937, killing 36 people.

The Airlander is essentially three streamlined airship-type bodies merged into one with wings and rotary engines.

It was built for the US military but the latter cancelled the contract after it was delivered.

Its makers, who have received a STG2.5 million ($A4.68 million) British government grant, now say they intend to build hundreds of the aircraft.

British Business Secretary Vince Cable said the “innovative” craft “has the potential to lead the world in its field”.