Air Niugini's flight attendants union in Papua New Guinea says all flights out of Port Moresby could be grounded on Friday if planned strike action goes ahead.
Around 100 members of the Air Niugini Flight Attendants Association are planning to begin a series of rolling stoppages in protest over working conditions.
The president of the union, James Anjo, says the airline is trying to enforce heavy crewing, or working for 16 hours at a stretch.
Mr Anjo says the airline has withdrawn overnight allowances for staff because they refuse to work for more than 14 hours at a time, as specified in their award agreement.
"We refuse to do heavy crewing and they're using the allowance as a bargain for us to do heavy crewing. And we didn't want to do heavy crewing any more, so they cut our allowances."
He says the union is key to settle the matter with airline management in-house.
Air Niugini managers were unavailable for comment.