Budget airline Ryanair is considering charging passengers to use the toilet on its flights.
Chief executive Michael O'Leary said the no-frills Irish carrier was looking at the possibility of charging STG1 ($A2.20) to enter its on-board lavatories.
"One thing we have looked at in the past, and are looking at again, is the possibility of maybe putting a coin slot on the toilet door, so that people might actually have to spend a pound to `spend a penny'," he told the BBC.
"I don't think there is anybody in history that has got on board a Ryanair aircraft with less than a pound."
Mr O'Leary defended the idea, saying the airline was always keen to find ways of raising "discretionary revenue" to keep airfares down and train stations often charged 20 pence ($A0.45) to use their public toilets.
Ryanair has a reputation for its high ancillary charges.
Passengers have to pay extra for such things as check-in luggage, most card transactions and refreshments purchased on board its aircraft.