Japan Air System (JAS), a unit of Japan Airlines System Corp, cancelled 120 domestic flights on Monday after it found cracks in engines made by Pratt & Whitney, a spokesman for the Japan Airlines (JAL) group said.
Pratt & Whitney is a unit of United Technologies Corp.
The spokesman for JAL, Asia's biggest airline, said it had discovered cracks in six engines used in five of the six planes it had inspected. The engines were models JT8D-217A and JT8D-217C and the planes were DC-9-81s and DC-9-87s.
The planes, which have two engines, were made by McDonnell Douglas, now part of Boeing Co.
The inspections were prompted by engine vibrations on a plane just before take off on January 6 and a case of engine trouble the following day.
Checks at Pratt & Whitney's New Zealand factory showed there were cracks in the engines' compressor parts, the JAL spokesman said.
Japanese aviation authorities have ordered JAS to check the remaining 19 of the 25 DC-9-81 and DC-9-87 planes it owns.
The inspections are due to end by Wednesday.
Pratt & Whitney was not immediately available for comment.
An industry source said no other Japanese airlines use the planes powered by the same engines, but an estimated 2,100 engines of the same models are in use globally.
The DC-9-81 and DC-9-87 planes, which carry between 134 and 163 passengers, are mainly used for short-haul flights. JAS, which generated 16 percent of the JAL group's total revenues in the year ended last March, has 57 planes fitted with various engines and may continue canceling some local flights after Tuesday due to the inspections and repairs. It could not yet estimate financial impact of the cancellations, the spokesman said.
Japan Airlines System was formed in October 2002 in a merger between Japan Airlines and JAS. It projected late last year it will post a net loss of 65 billion yen ($609.4 million) for the year to March, hit by the fallout from SARS and war in Iraq. The news appeared to have little effect Japan Airlines' shares, which ended Tokyo trade up 3.93 percent, outperforming a 1.65 percent rise in the key Nikkei average.