United Airlines' decision to ground much of its ageing Boeing 737 Classic fleet risks derailing Pratt & Whitney's potentially game-changing bid to pioneer cheaper parts manufacturing approval (PMA) alternatives to CFM International's aftermarket business.

United was the US launch customer for P&W's gambit in 2006, when the engine manufacturer declared it would develop spare parts for the CFM56-3, which is made by the rival GE/Snecma joint venture. Other airline customers include the UK's Jet2.com and an unidentified carrier in China.

But United's move in June to remove about 25% of its entire fleet - including 94 of its oldest 737-300/500s in a bid to slash capacity, has forced it to rethink the initial uptake of its critical engine PMA components.

Matthew Bromberg, P&W vice-president of global material solutions, says he is "disappointed", especially as the engine maker received the remaining three US Federal Aviation Administration supplemental type certificates in May approving life-limited parts for the high-pressure compressor, high-pressure and low-pressure turbines. These came less than two months after initial STC approval for the engine fan and booster.

"We have been through these cycles before. The 737 Classic is, however, a relatively young aircraft system and as there are no new Next Generation production slots for around five years, we're still predicting high demand and higher residual values for this aircraft, which has at least 15 years more life to it," says Bromberg.

He adds that P&W will work with United, whose 737s represented around 5% of an installed CFM56 base of 4,500 engines, half of which was "transactional". Bromberg says: "We would love to prove to United that they can save substantially on these parts." P&W, meanwhile, continues to work with the European Aviation Safety Agency and the Civil Aviation Administration of China on securing certifications for the PMA components.

Source: Flight International