The Irish Airline Pilots’ Association has claimed that Ryanair's corporate culture was responsible for three pilots on three flights issuing mayday calls on the same day last month.
The IALPA said that Ryanair’s league tables on the use of fuel led to the three planes making low-fuel emergency landings at Valencia Airport.
However, Ryanair has denied its fuel policy was responsible for the mayday calls on 26 July, when bad weather caused the flights to be diverted from Madrid.
It said the mayday calls occurred in extraordinary circumstances after more than an hour of extra flight time.
It added that the planes were not in imminent danger and landed with the required 30 minutes’ worth of fuel on board.
The Spanish Consumer Association has accused Ryanair of jeopardising passenger safety.
The Irish Aviation Authority and its Spanish equivalent are investigating the mayday calls.
Speaking on RTÉ's News at One, IALPA’s Evan Cullen said that Ryanair's corporate culture is putting pressure on pilots to make decisions they are not comfortable with.
Mr Cullen said: "These pilots came under the legal definition, the very regulations, of imminent danger, that's why the mayday calls were issued.
"The reasons why these guys hadn't enough fuel is because of the Ryanair policy and corporate culture with regard to fuel and the fuel policy."
However, speaking on the same programme, Ryanair spokesperson Stephen McNamara denied the claims.
He said the airplanes were not in imminent danger, but were required to make the mayday calls so that they could land with the required amount of leftover fuel.