Production issues plaguing Boeing Co.’s 787 Dreamliner “seem to have mushroomed,” with the planemaker and U.S. regulators still grappling to find an appropriate fix, according to John Plueger, chief executive officer of Air Lease Corp.

“There’s just greater and greater levels of inspections going on,” Plueger, who heads the largest publicly traded U.S. aircraft lessor, said on an earnings call Monday. “As yet today, it’s difficult to see a definitive fix that is agreeable by the aviation authorities and all going forward.”

Boeing hasn’t delivered any of the advanced aircraft since October while it inspects and repairs tiny imperfections that have cropped up on the interior lining of the jets’ carbon-fiber airframes. With about 80 Dreamliners sitting in storage, restarting deliveries is crucial to the company’s turnaround after it burned through about $20 billion last year.

Dave Calhoun, Boeing’s CEO, said last month that the company aimed to resume Dreamliner shipments during the first quarter with “most likely very few, if any in February” and clear most of the jets in inventory this year. Company representatives couldn’t immediately be reached for comment on Plueger’s remarks.

Some of the wide-body jets due to be delivered to Air Lease have been delayed more than 12 months, giving the Los Angeles-based company and its customers the right to bolt from their original contracts, Plueger said. Engineers are still verifying that the engineering tolerances for roughness wider than a hair’s breadth and shims—the filler for the tiny gaps or wrinkles—won’t pose any threat to safety.

“It’s still an unfolding story,” Plueger said. “I wish I could say definitively that there’s an end to it.”