On an investor call last month, the American Airlines chief executive, Doug Parker, predicted that the carrier would not resume Max flights before late December if the order came in November. Southwest Airlines and United Airlines have said they probably will no fly the plane until next year.
“Our process is going to be deliberate, structured, and we’re expecting it to take three to four months between an ungrounding and the aircraft being in revenue service,” Mike Van de Ven, the chief operating officer of Southwest, a major Boeing customer, said on a call with investors last month.
Nonetheless, the F.A.A. decision removes some uncertainty as Boeing seeks to rehabilitate its reputation, start fulfilling longstanding orders for the Max and gauge how soon and how fully air travel will recover.
The company has lost more than 1,000 orders this year, mostly for the Max, after accounting for orders that either were canceled or are likely to fall through. Aircraft contracts typically allow buyers to cancel or renegotiate terms if deliveries are delayed, adding to the urgency for Boeing to resume delivering the planes. Still, the company has more than 4,200 orders in its backlog, most of them for the Max.
The single-aisle plane is the latest in Boeing’s 737 line, an industry workhorse widely used by airlines around the world for short to intermediate distances. Southwest, for example, has more than 730 planes, all of them versions of the 737, including 34 Max jets. The airline has more on order, but its chief executive, Gary Kelly, said this week that Southwest was in no rush to expand its fleet.
For decades, Boeing had taken an incremental approach to the 737, choosing to update the plane rather than conceive a new model. That strategy had benefits, including reducing the need for costly pilot retraining. But it also resulted in a patchwork design that sometimes required workarounds. MCAS — for maneuvering characteristics augmentation system — was one such feature, developed to compensate for the size and placement of the engines on the Max.