A QANTAS captain was forced to relinquish the controls of a passenger jet last week just minutes before it was due to take off from Sydney Airport after cabin crew suspected she had been drinking alcohol before the flight.
Qantas has since launched an investigation into the incident after the senior pilot recorded a positive reading for alcohol.
The captain has been withheld from operational duties on full pay, but the airline will not comment on what reading she gave or how recently before the flight she had been drinking.
The incident occurred last Monday as the Qantas aircraft was about to depart for Brisbane. Flight attendants on the Boeing 767-300 aircraft, which can carry 254 passengers, informed the airline's flight operations managers that they suspected the captain of the plane had been drinking.
The aircraft had already been pulled back from the domestic terminal and was taxiing towards a runway for take-off when Qantas management made the decision to stand down the captain from command of the plane.
The 767 returned to the domestic terminal where the captain was taken off the plane and a replacement pilot was found to fly to Brisbane.
It is rare for pilots to be removed from flying for breaching airline procedure. Qantas has a zero tolerance to pilots recording an alcohol reading of any level.
Fewer than 100 of Qantas's 2200 pilots are women.
The investigation into the captain's alcohol reading is expected to take at least a month. Qantas has informed the air safety regulator, the Civil Aviation Safety Authority, of the incident.
However, it is considered a matter for Qantas rather than the regulator because the testing of the captain was done under the auspices of the airline's drug and alcohol management plan. If it is determined to be a one-off incident, the pilot will be expected to undergo counselling and later a medical assessment to determine whether she is fit to fly.
But if it is a long-term problem, she will be suspended from duties.
CASA has been conducting random breath tests of pilots, flight attendants and ground crews at airports since 2008. The rate of positive tests is understood to be very low.
A Qantas spokesman confirmed that a captain had been ''withheld from service for administrative reasons'' last week but he declined to comment further because the matter was under investigation.
A spokesman for CASA said yesterday that it would not comment on any specific testing carried out by an airline, nor on the results of any test.
"Anyone found to be affected by alcohol or drugs while performing, or when they are available to perform, safety-sensitive aviation activities will automatically be suspended from duties," he said.
"They are not able to return to duty until they have been … given a medical clearance."