The engineers' union has doubled down on demands Qantas inspects its entire Boeing 737 fleet after a low-cost Indonesian carrier found cracks in the "pickle fork" wing structure of two newer aircraft.
Lion Air this week found cracks in two Boeing 737s below the mandatory checking threshold of 22,600 landings, known as cycles, according to Indonesian media.
Australian Licensed Aircraft Engineers Association federal secretary Steve Purvinas says this vindicates his belief cracks could be found in any 737 aircraft.
Qantas last week pulled three of its 75 Boeing 737s from service after finding pickle fork hairline cracks, but says it isn't obliged to check other planes that have undergone fewer than 22,600 cycles.
The pickle fork is the structure between the plane's wing and fuselage.
"Cracks can appear at any time in the life cycle of these aircraft and there's no excuse why all airlines shouldn't be checking them to make sure their aircraft are safe," Mr Purvinas told AAP on Friday.
"I wasn't surprised at all that Lion Air had found cracks on aircraft below the 22,000 threshold.
"What did surprise me was that a low-cost carrier in Asia was actually checking these planes and Qantas, who says they put safety first, refused to check theirs."
Qantas has checked all 33 of its 737s with more than 22,600 flights, but Mr Purvinas wants Qantas to check the remaining 42.
"It's inevitable that they're going to find some cracks on the other 42 they haven't checked," he said.
While Virgin has found no cracks in its 19 aircraft checked above 22,600 cycles, Mr Purvinas also wanted Qantas' main rival to check all its 737s.
The US Federal Aviation Administration earlier this month ordered airlines to check within a week any 737s that had completed more than 30,000 cycles. Planes with more than 22,600 cycles must be checked within seven months.
"They've already checked all of their aircraft over 18,000 flights, but like Qantas they too should check all of their aircraft, as should every airline in the world," he said.
Qantas last week said the three affected planes would return to service by the end of the year, and the airline would work to minimise passenger disruption.
"Qantas will never fly a plane if we do not believe it is safe to do so," Qantas Domestic chief executive Andrew David told reporters in Sydney.
"Our entire reputation - our brand - is built on our safety record."