Australian low-cost carrier Tiger Airways Australia will remain under "heightened surveillance" by the country's safety regulator, despite the lifting of the airline's suspension.
Tiger was due to resume flights on 12 August following the lifting of a ban that has seen its 10-aircraft fleet grounded since 1 July over what the Civil Aviation Safety Authority (CASA) described as a "serious and imminent risk" to safety.
CASA said the airline has demonstrated compliance with a number of requirements - notably to put its 110 pilots through simulator training and testing - before being allowed to fly again.
The regulator has also imposed a number of additional conditions on the carrier's air operator's certificate, mostly around pilot training and proficiency, rostering and fatigue management, and documentation of that. It must also employ additional personnel in key positions and improve its safety management system, said CASA.
Tiger is limited to flying a total of 18 sectors per day for the rest of August. Prior to the suspension it flew around 60 sectors daily.
CASA had put the airline under routine surveillance late last year. The findings of that investigation led to the issue of a show cause notice in March.
Despite this, it went on to perform two flights below safe operating limits into two airports and, as a result, the airline was grounded on 1 July.
"It's not what happened on those individual flights, but what that told us about the training and proficiency of Tiger," said CASA.
"We had reached the position on 1 July where we had lost confidence in the airline being able to continuously manage safety. Once we had reached that point we had to put them on the ground."
Pilot training was a key issue to address, said the regulator, as it had concerns both about induction and continuous training. "We weren't satisfied that it was being performed to the standards we expect and we couldn't verify it from the documentation," it said.
Safety management systems were "inadequate", said CASA, particularly in the area of fatigue management. Although there was no evidence that pilots were working excessive hours, it said, "we couldn't verify that through their documentation".
CASA believes that the problems were caused by the airline's rapid growth. "It was apparent that the safety systems and resources hadn't grown at the same pace as the fleet, pilots and operations," it said.
The airline will remain under "heightened surveillance" over the coming months. CASA inspectors will be present in cockpits for some flights, as well as monitoring take-offs and landings from the ground, in addition to regular audits of paperwork.
"If there's any breach of the conditions we will take that very seriously and consider what the appropriate action might be."