Ryanair has said it operates to the highest European safety standards and rejected that there was any substance in the allegations made in the Channel 4 Dispatches programme aired last night.
The airline, Europe's biggest low-fares operator, has notified the Irish Aviation Authority (IAA), which regulates Irish airlines, of the allegations, and it has investigated whether safety breaches occurred.
Speaking before the programme was aired, a spokeswoman for the IAA said it has fully investigated three alleged safety breaches on Ryanair flights referred to in the programme and dismissed them.
The IAA spokeswoman said yesterday that the body had no concerns that Ryanair breached safety standards as claimed in the programme.
One of the incidents investigated was that a flight from Knock to Stansted took off after the door slide on the emergency exit showed a fault which was reported to the cabin supervisor. The IAA spokeswoman said it investigated that aircraft, examined its records and carried out a physical check and was satisfied no security breaches occurred.
The IAA said it was also satisfied about the circumstances in which a Ryanair flight took off from Forli in Italy despite having a faulty GPS system.
The spokeswoman said it is acceptable to fly when one or two GPS systems are not working, because there are others as a back up.
The aviation authority also said that a potential danger posed to a passenger in seat 1A was "not an issue".
The programme's undercover reporter, Charlotte Smith, secured a job as a member of Ryanair's cabin crew. She claimed that during her training her class was told that - in the event of a crash - a person who sits in seat 1A on a Ryanair aircraft will "probably die on impact" because a protruding piece of metal used to attach a stairs handrail would go straight into their head.
The IAA spokeswoman said that Ryanair doesn't determine the seating pattern on its aircraft, which is approved by international aviation authorities.
The airline no longer uses the Boeing 737-200 aircraft referred to but these are used by Brittania and Lufthansa and are approved by the regulatory authorities.
"This is not an issue," according to the IAA.
The documentary contains footage secretly filmed over five months by Ms Smith and reporter Mary Nash, who both secured jobs as cabin crew with Ryanair last year.
It shows cabin crew sleeping on board flights and complaining of fatigue.
A pilot told one of the reporters that if he refused to fly because he was tired he would "probably be fired and definitely demoted".
Ryanair said its pilot and cabin crew rosters minimise the possibility of fatigue and that pilots don't work for more than 900 hours a year - which averages at 18 hours a week. It said its cabin crew rosters also disprove the programme's claims.
The IAA said it regularly carries out audits of all operational aspects of Irish airlines. It said it has not found evidence of pilots exceeding their maximum hours.
The programme highlighted the fact that a number of cabin crew were on temporary security passes and that there had been no checks into a possible criminal record.
One pilot, filmed during a two-hour flight delay, said he didn't care about the passengers, who were facing being diverted from Stansted to Luton airport.
"You pay nothing for your ticket and you get nothing," he told the undercover reporter.
Ryanair yesterday announced another seat sale, offering three million free seats for travel during February, March and April.