MONTREAL - Porter Airlines said its fleet of almost two dozen Q400 aircraft has been given a clean bill of health after it conducted precautionary inspections recommended by Bombardier to search for cracks in a part located near the landing gear.

"All of our aircraft now have been inspected and are considered safe to operate," Robert Deluce, CEO of Toronto-based Porter, said in an interview.

"We have not found any issues that were highlighted in the inspection itself and our fleet seems to not be affected in any way."

Bombardier said 74 per cent of its Q400 planes needed to be inspected as a precautionary measure after one airline found cracks in the rear spar nacelle, a part near but not related to the functioning of the landing gear.

About 222 of the 300 planes in operation should have the nacelle fittings inspected for corrosion, fatigue and stress, the Montreal-based manufacturer (TSX:BBD.B) said Monday.

The aircraft's main landing gear is attached to the nacelle, which is the cover that houses the engine.

"This part that is being inspected has nothing to do with the extension or retraction of the main landing gear system," spokesman John Arnone said in an interview.

He said about 60 per cent of the aircraft have been inspected since Bombardier first issued a service bulletin in April, followed by another in July. The Q400 entered service in 2000.

"This is a precautionary and prudent measure undertaken by Bombardier and its customers," Arnone added.

Australia's Qantas Airways grounded five of the 21 Q400s operated by regional airline QantasLink after low-cost British carrier Flybe raised concerns about the fittings on its fleet of Q400s.

Qantas told local media that it would take three to four weeks for the work to be completed on the five planes, which are its oldest Bombardiers. It said two teams of engineers from Bombardier would travel from Europe to repair any cracking.

Arnone said he was not aware of other airlines removing their planes from service while the company conducted inspections.

He said the aircraft remains safe and the potential problem is unrelated to incidents in 2007 that resulted in emergency landings in Denmark and Lithuania.

The emergency landings by Scandinavian Airlines planes were subsequently found to be caused by the corrosion of a bolt that prevented the landing gear from locking. Arnone said the bolts and the nacelles are made by two different manufacturers.

The airline removed its fleet of Q400s from service following the second crash in October 2007.

As one of the largest operators of the Q400s, Porter has a lot at stake with any concerns about the safety of the aircraft. Deluce said he has full confidence in the plane and hopes to add 10 more of the aircraft over the coming years to the 20 it now operates.

"It's an airplane that we consider to be highly reliable and certainly has done a very good job for Porter," he said, noting that everyone was being very proactive concerning the inspections.

Deluce called the SAS issue a "red herring" since the problems were confined largely to its fleet and caused mainly by that airline's maintenance issues rather than any systematic problems with the plane.

He noted that SAS turned around and purchased newer Next Generation versions of the same aircraft after grounding its fleet.

Meanwhile, U.S.-based Frontier Airlines said it would retain three Q400 turboprops to service flights in Colorado, including to Aspen. The subsidiary of Republic Airways Holdings Inc. had planned remove the fleet but a separate lease arrangement apparently fell through.

Bombardier shares slipped 10 cents to $4.46 Monday on the Toronto Stock Exchange.