For safety reasons, up to 50 Boeing 737 NG (Next Generation) aircraft are kept on the ground because of the possibility of cracks on a major component. This family of aeroplanes comprises the 737-600 to 737-900 models.
A Boeing spokesman said that less than five percent of the 1000 aircraft surveyed worldwide had test results that prevented them from taking off for the time being. Affected is a component, the pickle fork, which connects the wings to the fuselage.
The US Federal Aviation Agency (FAA) this month ordered the inspection of the 737 NG aircraft that flew more than 30,000 times, after the discovery of such structural cracks on a plane in China.
Qantas is currently holding 33 of its 737 NG aircraft on the ground as a precautionary measure before further testing.
UPDATE on Qantas: Qantas says it has removed three 737s from service for repair following pickle-fork inspections. The airline has completed inspections on 33 of its aircraft with more than 22,600 cycles.