Qantas acted unlawfully, abandoned its duty of care and exposed one of its pilots to a potential breach of Chinese immigration law when it offloaded him and his son in Hong Kong over an industrial matter, the pilots' union says.

The Australian and International Pilots Association accuses Qantas of breaching industrial protections in the Fair Work Act, leaving the pilot to fend for himself under questioning by Hong Kong's immigration officials last Friday.

Qantas has a fundamental obligation to all its pilots to return them to their home base, the union's executive director, Philip van den Heever, wrote to the airline.

On Friday, Qantas stood down one of its pilots, Captain Steven Anderson, from flying duties on the QF30 Hong Kong-Melbourne flight, and his son was erased from the passenger list, leaving them in the Chinese territory.

Qantas removed the pilot from duty after the union gave notice Captain Anderson - also the union's secretary - would work to rule and not undertake flying hours beyond the normal shift.

Qantas explained in a written response to the union yesterday that Captain Anderson was removed because the airline would not accept partial performance of his duties and was removed lawfully under the terms of the Fair Work Act.

Our priority was to get 307 passengers to Melbourne as quickly as possible, Qantas spokesman Luke Enright said yesterday.

How Captain Anderson's son also lost his flight booking remains contentious: last Friday Qantas told Fairfax Media the son's booking was cancelled at his own request, an assertion that Captain Anderson described as absolutely a lie.

Qantas has since written to the union denying it had any knowledge of telling a journalist that the pilot's son requested his booking be cancelled.

The airline now says the son could not fly on QF30 because the staff discount ticket he was booked on required his father to be on duty in the plane.

Captain Anderson said he faced increasingly tense questions from Chinese immigration officials about the uncertainty of his status in Hong Kong, as he tried to leave the country with his son without the correct airline paperwork.

But Qantas said it provided a copy of the necessary paperwork to the pilot.

The airline said yesterday it would not reimburse the pilot, or his son, for any expenses for their stay in Hong Kong and return to Australia and would dock the pilot's pay.

The industrial wrangling comes as Qantas axes its in-flight safety video briefing by Hollywood actor and Qantas ambassador John Travolta, where the Hollywood star extolls the virtues of the company's pilots.

With Qantas ... preparing to announce moves to replace Australian Qantas pilots with outsourced and offshore alternatives on August 24, Travolta's message has been deemed inappropriate for the times, union vice-president, Captain Richard Woodward, claimed.

Qantas said it had always intended the video would have a limited span.