Sydney - The astonishing run of maintenance woes for Australia's Qantas Airways Ltd continues with a faulty rudder delaying a plane from London for 15 hours and an internal flight forced into an unscheduled landing because its toilets hadn't been emptied.

Qantas confirmed Monday that a "technical issue" with the rudder on a 747-400 had resulted in Sydney-bound passengers spending an extra night in London.

Almost as annoying for passengers was Sunday's impromptu stop in Adelaide after ground staff in Sydney forgot to empty toilet tanks on a flight that was bound for Perth.

"Four out of seven toilets were not flushing so for the comfort of our passengers we diverted to Adelaide," a Qantas spokesman said.

Last week engineers at Singapore's Changi Airport discovered a body panel had fallen off a Qantas jumbo flying between Melbourne and the island republic forcing a six-hour delay for London-bound passengers.

On Wednesday a Qantas Boeing 767 left a trail of hydraulic fluid on the tarmac at Sydney Airport after it touched down after a flight from Melbourne.

Australia's aviation safety watchdog, the Civil Aviation Safety Authority (CASA), is investigating fleet maintenance at Qantas.

The probe was sparked after a serious safety scare July 25 when an exploding oxygen tank in the cargo bay punched a 3-metre hole in the fuselage of a Qantas 747-400 flying from Hong Kong to Melbourne.

The pilot descended from 29,000 feet to 10,000 feet in about five minutes and made an emergency landing in Manila without the benefit of the full suite of instrument landing systems.

A week later a domestic flight was forced to return to Adelaide after a wheel bay door on a Boeing 767 failed to close properly.

Just days after that, a flight bound for Manila returned to Sydney after the pilot declared an emergency and dumped fuel because of a leak in the hydraulics operating a wing flap.

Transport Minister Anthony Albanese urged Australians not to "talk down" Qantas, declaring it had one of the safest aviation systems in the world. The CASA report is expected to be delivered to the government next week. (dpa)