Southwest Airlines announced Thursday it's suspending Boeing 737 Max flights through much of the busy summer travel season.
The announcement grounds the planes until August 5, two months longer than initially planned.
In an update posted online, Southwest President Tom Nealon said the decision was made "to further increase the reliability of our schedule and reduce the amount of last-minute flight changes – especially during the upcoming summer travel season."
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Nealon said customers booked on those trips are being notified so they can reschedule flights well ahead of their travel date.
Hours earlier, Boeing CEO Dennis Muilenburg spoke at the Bush Institute Leadership Forum in Dallas.
He vowed to rebuild public trust amid one of the worst corporate crises in history.
"All of us feel the immense gravity of the events across our company and frankly, these last few weeks have been the most heart-wrenching of my career," Muilenburg said.
In both cases, investigators said a damaged sensor sent bad data to a new system called MCAS. MCAS then pushed the noses of both planes down to pick up speed.
Denny Kelly was a flight captain for nearly 50 years.
"From the people that I know that are involved in this thing, they've got the fix. They know exactly what to do and they're fixing the airplanes. What they've got to do is to get the FAA to certify it," Kelly said.
A timeline for when the fleets can fly again remains unclear.
American Airlines still says its 24 Max planes will return to service June 5, a date Kelly expects to be also pushed back.
Southwest said the majority of customers itineraries are unaffected by the cancellations.
Still, travel experts are encouraging passenger taking a Max plane to contact the airline right away to get rebooked.