Pilots at Europe’s biggest low-cost airline Ryanair feel inhibited from reporting safety concerns and want regulators to establish the impact on safety of its employment practices, a group of pilots seeking union representation said on Monday.

The Irish carrier has become famous for its low-fare no-frills service which has led to controversial additional charges for everything from paying by most normal cards, checking in at the airport, carrying hold bags and reserving seats.

But the unofficial Ryanair Pilot Group (RPG) said it had polled more than 1,000 pilots and first officers, over a third of the airline’s total, and found 94 percent wanted regulators to conduct an inquiry into the impact of employment practices on safety.

It also said 89 percent did not consider that the airline had an open and transparent safety culture and two thirds were not comfortable raising issues through an internal reporting system.

Ryanair declined immediate comment, but said in its annual report at the end of last month that it has not had a single passenger or flight crew fatality in its 29 years of operation and that it encourages flight crews to report any safety concerns through its Safety Alert Initial Report system or to use an online confidential system.

“Ryanair has no comment at this time,” a spokeswoman said.

RPG’s chairman, Evert van Zwol, who is not a Ryanair pilot but until recently was president of the Dutch Airline Pilots Association (VNV), said some three quarters of Ryanair pilots are employed through agencies and nearly all of these are on so-called zero-hour contracts, which offer no guaranteed work.

The Irish Airline Pilots’ Association trade union said these contracts had some of the worst conditions in the industry.

That could mean pilots may shy away from speaking up, for example on whether their plane was carrying enough fuel, or choose to fly when sick, van Zwol said.

While there was no proof that this was the case, the concerns warranted a full independent inquiry to establish if there were any grounds for safety concerns, he said.

The RPG said it gave the survey results to Ryanair and the Irish Aviation Authority (IAA).

“This needs to be followed up by someone independent,” Van Zwol said. “It’s mind-boggling that these people are not taking a pro-active stance – what could possibly be wrong with a pro-active investigation?”

The IAA declined to comment.

Last year the IAA launched an investigation following emergency landings by three Ryanair planes in Spain after they approached their minimum required fuel.

The report found the planes were carrying more than the minimum, but recommended the company review its fuel policies for planes flying into some busy airports during poor weather conditions.

Britain’s Channel 4 television is due to broadcast a documentary later on Monday about Ryanair, in which it says it speaks to pilots on their concerns about passenger safety, including fuel policy and working conditions.

(Additional reporting by Conor Humphries; Editing by Greg Mahlich)

Photo Credit: A model airplane rests on a table during Ryanair's announcement of its commitment to purchase aircraft from Boeing, in New York March 19, 2013. Lucas Jackson / Reuters