Australia’s Civil Aviation Safety Authority (CASA) has grounded Transair, the carrier that had been under investigation following last year’s fatal crash of a passenger aircraft.

“Today we took it to the next level which is an immediate suspension of the air operator’s certificate (AOC). So Transair has been grounded since late last night,” CASA says from Canberra. Transair AOC was held by a holding company Lessbrook. A statement says: "CASA has reason to believe the operator had engaged, may be engaging and was likely to engage in conduct constituting, contributing to or resulting in a serious and imminent risk to air safety".

This is only the second time CASA has taken such action under the current legislation, according to the authority.

CASA now has five days during which it has to lodge a case with Australia's Federal Court in order to have the grounding extended for another 40 days, says CASA.

The authority late last month sought to cancel the Brisbane-based airline’s AOC but the airline appealed so it had been operating while waiting for its case to be heard in the Administrative Appeals Tribunal.

But CASA was able to have the airline grounded with immediate effect because it alleges Transair posed “an immediate threat to aviation safety”, says the spokesman.

“Late on Friday [24 November] we got some new information with regards to the flight operations side of the airline,” he says.

“It had to do with issues of flying operations, operations of the pilots and the systems that go around that.”

He says CASA’s previous investigations had focused on maintenance and control issues.

Transair has been under investigation on several occasions over the years but it came under even more scrutiny following the May 2005 crash of a Fairchild Metroliner.

The crash killed all 15 people on board, the worst civil aviation accident in Australia since 1968.

According to Transair’s website it still has at least six other aircraft, mostly Metroliners, and has been providing scheduled and charter services.

Transair executives were unavailable today.