On Oct. 29, Europe's air safety regulator expressed deep concern following the latest crash landing of a Scandinavian Airlines turboprop plane - the third in less than two months involving the same type of commuter aircraft.

"We are very concerned about this most recent Dash-8 Q400 accident and the possible relation with other accidents involving the same plane," said Daniel Holtgen, a spokesman for the European Aviation Safety Agency (EASA), referring to the twin-engined plane made by Bombardier Aerospace of Canada.

Holtgen said that the agency, based in Cologne, had requested an emergency meeting with Bombardier and Canadian transportation safety officials to discuss the possibility of a new grounding order.

The board of Scandinavian Airlines, or SAS, announced earlier that the carrier would permanently discontinue use of its 27 Q400 planes, after a flight from Bergen, Norway, with 44 people on board, crash landed in Copenhagen on Oct. 27. Its main landing gear had failed to extend. No one was seriously injured in the accident, which followed two in September where the airline's Q400s skidded off runways in Denmark and Lithuania because of a landing gear failure.

The European agency said it had offered to assist the Danish authorities.

"What is important is for us to get the details fast," Holtgen said. But he stressed that any European decision affecting the plane's authorization would be made in close coordination with Transport Canada, the regulator that certifies all Bombardier aircraft for safety.

"We do not want to do anything unilaterally," Holtgen said.

Spokesmen for Transport Canada and Bombardier said they would seek to organize a meeting as soon as possible.

Separate investigations last month by the Danish and Lithuanian authorities concluded that the two earlier Q400 accidents, on Sep. 9 and Sep. 12, had been the result of corrosion of a specific landing gear component.

Hans Ollongren, a spokesman for SAS, said that the incident on Oct. 27 did not appear to be related to the previous two.

"In the first two cases, the reason for the collapse was the corrosion in a component that was not subject to inspection according to the manufacturer's maintenance manual," he said. "In Copenhagen, it was the case that the main landing gear did not extend properly."

Bombardier has said it is "disappointed" that SAS has chosen to discontinue operating the Q400 before the Danish authorities had concluded their inquiry.

Lucy Vignola, a Transport Canada spokeswoman, said on Oct. 29 that the regulator was awaiting further information from the Danish investigation before issuing any advisory to operators of the plane.

Following the two SAS crash landings in September, Transport Canada ordered the grounding of more than one-third of the 160 Q400s in operation worldwide pending a detailed visual inspection of the main landing gear as well the mechanism used to extend and retract it.

Air safety experts said it was unusual for aircraft landing gear assemblies to break or to fail to extend fully.

"It is not a common incident," said Fred Mirgle, the chairman of the aviation maintenance science program at Embry-Riddle Aeronautical University in Daytona Beach, Florida, U.S. "If you have a landing gear that fails, the potential can be disastrous."

Mirgle said that incidents involving landing gear generally involve problems like tire failures that typically do not cause forced landings or damage to aircraft.

SAS - the joint flag carrier of Sweden, Denmark and Norway - said its decision to stop flying the Q400 had led to the cancellation of more than 200 flights since Oct. 28. Ollongren said the carrier planned to replace the affected planes with others from its 300-plane fleet as well as leased aircraft. The process would take several months to complete, he said.

The airline estimated that discontinuing Q400 services could cost it as much as 400 million Swedish kronor, or US$63 million, through the end of 2007.

Twenty-six airlines operate the 78-seat Q400, which entered commercial service in 2000. The SAS Q400 fleet is the second-largest in Europe after the British low-cost carrier Flybe, which operates 29.

A spokeswoman for Flybe could not be reached for comment about the carrier's plans for its Q400 fleet. Austrian Airlines, which operates 10 of the planes, said its trust in the plane remained "unbroken," while Augsburg Airways, a unit of Lufthansa with a fleet of six Q400s said that it, too, would continue to fly its turboprop fleet.

The U.S. regional carrier Horizon Air has 33 of the planes. Dan Russo, a spokesman for the airline, based in Seattle, said it planned to continue flying its turboprop fleet unless advised against it by Bombardier or air safety regulators.