Qantas risks the grounding of parts of its fleet if the current dispute with licensed engineers and mechanics raises doubts over the integrity of maintenance releases clearing its jets to fly.

This morning at Melbourne Airport a shift comprising six members of the Australian Licensed Aircraft Engineers Association was reportedly excluded from their workplace and replaced by managers and contractors.

The issue for Qantas as it struggles to keep to its promise to fly all passengers on the day, but not necessarily the hour of intended travel is the legal requirement for a licensed engineer to observe and direct all the work on being done on an aircraft ‘at all material times.’

Pilots have reminded Crikey that in the US recently significant numbers of jets flown by Southwest Airlines and American Airlines were grounded while a backlog in repairs and the associated trail of dockets that verified each step of the processes that are enforceable in law were rectified.

A spokesperson for CASA also reaffirmed that Qantas jets flying with time-limited defects, which in some cases exceed over 50 items on Qantas aircraft, would have to be withdrawn from service until they were brought up to date as the deadlines fell due.

It is not known what proportion of the Qantas fleet is going to run out of time in coming days.

However, CASA is understood to have told its inspectors to closely examine all documentation to ensure that all faults and repairs are being written up and acted upon.

The crisis has been caused by the licensed engineers refusing to work overtime in support of a pay dispute with Qantas.