Qantas said the six B737-400s would be removed from service while the airline cross-checked maintenance records relating to work carried out at one of its Australian facilities.
The company's senior engineering manager said it was a record-keeping issue and there were no safety implications.
"What we picked up is a step in the maintenance check which does not look like it has been completed, and that's why we've got to go back and verify that," David Cox said.
"Until we are absolutely certain that everything is 100 per cent correct we cannot operate the aircraft," he told the Australian Broadcasting Corporation.
Three flights were cancelled on Tuesday night.