Updated

A Qantas pilot was under investigation Tuesday over a mile-high scandal with a female passenger during a long-haul flight to Australia.

Passengers in the first class section of QF32 from London were stunned at the pilot's amorous antics with the woman.

He was seen sitting on her lap during the flight in the luxurious premium section of the Qantas A380 jet before things became quite steamy, sources told the Herald Sun.

The seat has privacy walls and reclines to become a bed. The pilot was off-duty and not in uniform at the time of the incident.

He was scolded twice by the crew as passengers became annoyed at the public display of affection, sources said. After the flood of complaints, the pilot shifted to economy.

The female passenger left the flight in Singapore and the pilot returned to the first class cabin, staying on the flight until it landed in Sydney at 8:10pm on Friday.

It was unclear whether the pilot knew the woman before boarding the flight, or if he was intoxicated.

Qantas said an investigation was underway that could cost the pilot his US$237,288 a year job.

"Qantas is aware of an incident involving a traveling crew member on board QF32. The matter is being investigated internally in line with Qantas policy," a spokeswoman said. "Interaction of that nature is something that wouldn't be sanctioned."

It is not the first time that amorous behavior on a Qantas flight has hit the headlines.

Actor Ralph Fiennes was sprung in a tryst with former Qantas hostess Lisa Robertson in January 2007.