Airlines are considering suing Airbus after the aircraft manufacturer warned them that the front-end of the A340-600 was dangerously overweight, The Times has learnt.

The problem is caused by heavier than expected first and business-class areas and airlines have been told to reduce the amount of cargo they carry to rebalance the aircraft.

The first and business class sections on some A340-600s are so heavy that they are pushing the jet's nose down during flight, which can play havoc with the aerodynamics and potentially endanger passengers and crew. Flying nose down also increases drag off the wings and forces the aircraft to burn more fuel.

Airbus has recommended that airlines carry about five tonnes less cargo in the front of the plane to compensate, a reduction of nearly 10 per cent in its total cargo capacity.

Airbus says that the airlines are to blame for fitting premium cabins with full-sized beds, heavy furniture and weighty entertainment systems.

However, aviation sources have told The Times that a number of airlines are insisting that it is Airbus's error. The airlines believe Airbus has incorrectly stated the maximum weight for front-end cabins and they are considering suing for lost cargo income.

Recent estimates show that a commercial airliner flying one tonne overweight costs the equivalent of 12 passengers everyday. Assuming that the A340-600s are flying five tonnes overweight, each jet is losing income equivalent to 21,900 passengers a year.

If the airlines can prove their case, they could claim hundreds of millions of dollars in compensation from Airbus.

The A340-600 is flown by numerous airlines with Virgin Atlantic, Lufthansa and Iberia operating the largest fleets. These airlines were unavailable for comment on April 7.

An Airbus spokesman said: "As premium cabin interiors become more customised, the added weight of customisation must also be taken into account as a factor in the overall loading of the aircraft. A heavier cabin in the front section where premium cabin products are normally placed therefore could reduce the cargo loading capacity in that section."

The A340-600, at 75 metres, is longer even than the A380, and typically seats 380. Doug McVitie, the director of Arran Aerospace, said: "The A340-600 is a piece of spaghetti with wings. Anything heavy at the front will therefore throw off the centre of gravity and that causes all sorts of problems."