The low-cost airline would charge passengers less on "bar stools" with seat belts around their waists.

Michael O'Leary, the chief executive, has already held talks with US plane manufacturer Boeing about designing an aircraft with standing room.

He is now seeking approval from the Irish Aviation Authority before ordering a new fleet of carriers, according to The Sun.

A Ryanair spokesman told the newspaper: "If they approve it, we'll be doing it."

Mr O'Leary is reported to have got the idea from the Chinese airline Spring, which has put forward similar plans. It estimates space could be made for up to 50 per cent more passengers and costs could be cut by 20 per cent.

It is not the first time Ryanair has come up with a controversial proposal for cutting costs. Earlier this year Mr O'Leary suggested passengers could be charged �1 to use the on-board lavatories.

In an interview on BBC television he said that the low-cost airline was looking at the possibility of installing a coin slot on the lavatory door so that "people might actually have to spend a pound to spend a penny."

Mr O'Leary also considered introducing a "fat tax" for overweight passengers.

"We are not considering standing-only accommodations, nor do we have any plans to do so," says spokesman Nick West. "Among other things, stringent regulatory requirements - including seats capable of withstanding a force of 16 Gs - pretty much preclude such an arrangement."

Sixteen Gs is 16 times the force of gravity, so the seats must be strong enough - and strongly secured enough - not to topple over like dominos in the event of a crash. Vertical seats would require more reinforcing than standard seats, because the passenger's centre of gravity is higher.

"More reinforcement means heavier planes which use more fuel, and that's the last thing Ryanair wants," says David Learmount, operations and safety editor of Flight International. "They'd end up having to reinforce the floor, and possibly the bulkheads too if the seats need to be secured top and bottom. And how many points of contact would the straps have to have? Across the body, perhaps securing the ankles, the knees, the head."

Which sounds like the Hannibal Lecter way to fly.