Exhausted pilots who land planes after being awake for 22 hours will feel as if they have drank "four pints of lager" and could fall asleep in mid-air, an Oireachtas committee has been warned.
The Irish Airline Pilots' Association (IALPA) raised safety concerns about proposed new European rules forcing them to work longer hours.
IALPA said the European Aviation Safety Agency (EASA) ignored its own scientific evidence over proposed extensions to standby and flight duties.
The association claims that the proposals fail to protect passenger safety and could have serious consequences.
IALPA safety and technical officer Capt Paul Cullen highlighted the risk of pilots falling asleep if proposed longer hours are introduced.
Under current rules, pilots can be on standby for about six hours, and can also be expected to be carrying out duties for a further 11 hours and 45 minutes overnight, including checking in at the airport and flying time.
However, under the new European proposals they will be expected to be on standby for up to eight hours, and could be on duty for another 14 hours, a total of 22 hours awake.
Having pilots awake for 22 hours on standby and flying duties was akin to having consumed four pints of lager, Capt Cullen said.
Pilots in mid-air did not have motorway rumble strips or motion sensors to alert them if they nodded off, he added.
Capt Cullen also told the Oireachtas Transport Committee that disruptive schedules interfere with pilots' body clocks and cause fatigue.
The EASA proposal disregarded unanimous scientific advice on the risks for pilots to operate an aircraft and land after having been awake for more than 22 hours.
IALPA president Capt Evan Cullen said one pilot in Ireland was put through a disciplinary process after he called in sick suffering from fatigue caused by the effect of working split early and late shifts.
He said as many as 30pc of pilots who suffered from fatigue did not report the condition.
"This is an ongoing issue with us," he said.
The proposed new regulation will also allow night flights of up to 12 hours while scientists recommend a limit of 10 hours.
Putting crews on open-ended standby for many days without an ability to plan their sleep, and evading stringent rules on flight schedules that disrupt sleep patterns are also major concerns.
The new rules, if implemented, will standardise practice across Europe, replacing all existing national schemes and affect all European pilots and cabin crew.
IALPA said all of the existing scientific research and data has highlighted the dangers associated with pilot fatigue.
Sinn Fein TD Michael Colreavy said he found the pilots' presentation "deeply disturbing" and expressed fears that short-cuts could be taken if profits fell. He was very concerned about claims that the European aviations safety agency had ignored its own scientific advice.