The state of Queensland's Barrier Aviation airline has been grounded by the Civil Aviation Safety Authority (CASA) after the airliner has been found to contain "serious and known defects." Effectively immediately, the suspension will last for five working days.

Peter Gibson, CASA spokesman, said an earlier safety audit made on the airline company and its fleet showed serious maintenance issues.

"CASA has evidence of Barrier Aviation directing pilots to fly with serious and known aircraft defects, as well as not recording those defects on aircraft maintenance documentation when the defects became known," Mr Gibson said said in a statement.

"The suspension follows an audit of Barrier Aviation, which revealed a range of maintenance related deficiencies."

The investigation on Barrier Aviation, which flies to Horn Island, Darwin, Gove Peninsula, Papua New Guinea and the Pacific Islands, was conducted for six weeks, but the more alleged serious maintenance problems were discovered only in the "past couple of days."

"This grounding was not in any way driven by the fact we're at the holiday season: it's business as usual; if we find serious safety matters we must act," Mr Gibson said. CASA noted it doesn't think the airline's grounding will have a major impact on Northern Territory travellers this Christmas.

"We're got no faith in the fact that the aircraft are being looked after in the way that they should be," he added.

The five-day operations deferment could stretch to another 40 days, Mr Gibson said, if the Federal Court approves to extend the suspension, while CASA makes further investigations.