Boeing CEO Dave Calhoun acknowledged the plane’s manufacturing flaws as more than 170 planes remain grounded for a fourth day.

He stressed that the company will ensure that an accident like the one that detached the door on the Alaska Airlines aircraft in mid-air “never happens again. »

It is the first public acknowledgment of error by Boeing since the accident occurred when the door plug broke on the nearly full 737 MAX 9 on Friday, leaving a gaping hole next to a – miraculously – empty seat.

Calhoun said he was “shaken to the bone” by the accident, which has reignited pressure on Boeing nearly five years after the plane safety crisis sparked deadly crashes in Indonesia and Ethiopia.

“We’re going to approach this problem as number one, recognizing our mistake,” Calhoun told employees, according to a quote released by Boeing. “We will approach it 100% and with full transparency every step of the way.”

Alaska Airlines ( ALK.N ) and United Airlines ( UAL.O ), the two U.S. carriers operating the planes in question, found loose components, raising fears that such an incident could have happened again.