Boeing resumes some 737 Max test flights

Boeing resumed flights of its new 737 Max jetliners on a limited basis at the weekend, setting the stage for the first commercial delivery after a potential engine flaw temporarily grounded the single-aisle aircraft.

Regulators cleared the planes to fly as long as they are powered by spare engines that do not include the possibly defective part, the Boeing spokesman Doug Alder said. The supplier CFM International, a joint venture of General Electric and Safran, alerted the plane maker late last week to a manufacturing quality problem with low-pressure turbine discs in the Leap engines.

Boeing is racing to inspect the engines and meet delivery commitments to Indonesia’s Lion Mentari Airlines, the largest Max customer. Lion Air’s delivery has been delayed four days, and it will receive the first one on May 22, said the director Edward Sirait. The Lion affiliate Malindo Airways will use the first jet.

"The plan remains to start deliveries this month," he said. Norwegian Air Shuttle is also slated to receive its first 737 Max in late May.

On Wednesday, Boeing revealed a possible quality or manufacturing defect in the Leap 1-B model, created specifically for the Max. The plane-maker hadn’t detected any issues with the low pressure turbine during more than 2,000 hours of flight testing. Boeing also had a small stash of Leap engines on hand that were unaffected, Alder said.

Inspectors will tear down and examine about 30 affected engines at facilities in the United States and France, said Rick Kennedy, a spokesman for GE. The components came from a single disc supplier, and the 737 Max planes being flown now use discs from two other manufacturers.