THE Dublin-born boss of Australia's Qantas has called Ryanair's plans to charge for toilets and for standing passengers "a great publicity stunt".
Alan Joyce described himself as "a bit of sceptic" about airlines installing stand-up seating or charging passengers to use toilets.
Ryanair chief executive Michael O'Leary this month announced a plan to remove the back 10 rows of seats from 250 planes and replace them with 15 rows of so-called vertical seating.
Instead of being allocated a seat, Ryanair travellers would perch on a narrow shelf and lean against a flat, padded backboard.
Two lavatories at the back could also be removed, helping to allow up to 50 extra passengers on each flight.
"I think charging for toilets and stand-up seating is going a bit far," Mr Joyce told reporters after an Asia-Pacific Aviation Outlook Summit in Sydney.
"It's a great publicity stunt, but the practicalities are that there are physical limits to how many people you can have on the aircraft because there are safety concerns."
Mr Joyce is a former chief executive of the Qantas low-cost offshoot, Jetstar.
But Mr O'Leary's ideas might be catching on in some low-cost airlines. Tiger Airways, which is backed by Singapore Airlines, yesterday raised the possibility of vertical seating or installing coin-operated toilets on its aircraft if it helped to lower fares.
But Mr Joyce said safety standards required passengers to be able to leave aircraft with 90 seconds with half the exits closed.
The short haul "workhorses" the Airbus A320 and the Boeing 737 -- used by Ryanair -- were also both at their limits in terms of trying to fit more passengers on board.
"Getting people to stand up for no economic reason doesn't seem to make sense," Mr Joyce added.
"You are into completely redesigning a new aircraft type before that ever would become feasible.
"I don't think there are many airlines that would be asking Boeing and Airbus for that particular design feature," he said.
Ryanair hopes to phase in the "perches" for stand-up passengers on commuter flights of up to an hour long before expanding them to all aircraft.
However, aviation law says that people have to have a seat belt on for take-off, landing and turbulence.
The European Aviation Safety Agency, based in Cologne, will have the final say on whether the perches meet the rules.