Four Ryanair pilots, speaking anonymously, made their accusations against the budget airline on a Dutch TV show, The Sun reported.
"There is pressure put on crews to take as little fuel as possible, in order to save money for the company," one pilot said.
Another added: "I hope it doesn't take a crash from one of our planes to wake everybody up."
The accusations by the pilots came after Ryanair was told to review its operating procedures when three jets had to make emergency landings in Valencia, Spain, on the same day due to low fuel.
On Sunday, a spokesperson for Ryanair said: "The claims made by this Dutch TV program are factually untrue. As the official report into the three Valencia weather diversions confirmed, all three pilots took extra fuel and all three aircraft fully complied with safety regulations. A joint statement issued by the Irish and Spanish safety authorities confirmed that Ryanair safety is 'on a par with the safest airlines in Europe.'"