Southwest said that without the planes, it will drop about 330 flights each weekday from its normal schedule of about 4,000 daily flights. That is a far higher number of cancellations than at other airlines, which don't own as many Maxes.
Southwest had previously removed the Max from its schedule through April 13. Now it won't use the plane through June 6. American Airlines and United Airlines, the other two U.S. carriers that own Maxes, had already dropped the plane from their plans until June.
Dallas-based Southwest is the world's biggest operator of Boeing 737s, with about 750 in its fleet. It has 34 grounded Max jets — more than any other carrier — and expected to get more by now, but Boeing halted deliveries in April, a month after the plane was grounded worldwide.
Southwest said it is continuing to get information about the plane's status from Boeing and the Federal Aviation Administration. Chicago-based Boeing is making changes in flight-control software and other systems on the plane after crashes in Indonesia and Ethiopia killed 346 people. The aircraft maker faces several more steps before winning FAA approval to resume flights.