Chicago-based Boeing reckons it can squeeze another 14 seats on to its best-selling 777-300ER long-haul twin-engine airliner by reducing the size of the toilet area. The traditional three-class cabin lay-out for the aircraft currently seats around 386 passengers, so the magic 400 mark could come within sight.

The move will maximise the appeal of the $330million aircraft to prospective buyers, but may not impress passengers who already struggle to do their business in cramped conditions.

The plans are part of the development of Boeing’s next generation 777X model. In addition to its smaller bathrooms, the new-look 777-300ER will also feature updated overhead lockers which will help reduce the weight of the aircraft by 1200lb. And redesigned wings will contribute to a 5 per cent reduction in fuel consumption. The new design will be unveiled at the Paris Air Show later this month.

Budget airine Easyjet recently announced plans to add an extra row of seats on its Airbus A320 aircraft, increasing the total number of seats from 180 to 186. But the airline insisted that passenger comfort would be improved by better-designed seats, and explained that the extra row of seats was made possible by using previously unused space behind a wall at the back of the aircraft, and by moving a loo.