Dozens of flights canceled at O'Hare amid fallout from door plug blowing off plane

CHICAGO (WLS) -- Dozens of flights are canceled at O'Hare airport Monday because of the grounding of the Boeing 737 Max 9 planes.

Also Monday morning, shares of Boeing tumbled 9% at the opening bell, as the fallout continues after part of a plane blew off midair last week, leaving behind a gaping hole and scared passengers.

Chicago-based United Airlines said 200 cancelations are expected Monday, dozens of which are out of O'Hare.

Investigators are looking into how a piece of metal ripped off mid-flight last Friday from an Alaska Airlines jet.

That missing door plug that flew off the plane was recently found.

The National Transportation Safety Board announced a schoolteacher in Portland, Oregon found the door plug, which is used to cover and seal optional emergency exits. The object landed in his backyard.

"We're going to go pick that up and make sure that we begin analyzing it," NTSB Chair Jennifer Homendy said.

Investigators had been looking for the plug for days after it blew off the plane in midair, forcing an emergency landing.

Air traffic control could be heard saying, "Alaska-Seattle, Alaska 1282, we've just depressurized, declaring an emergency. We need to descend down to 10,000."

Investigators said the door plug de-pressurized just after the plane took off, with 177 passengers and crew onboard.

The entire ordeal lasted 26 minutes.

Investigators were able to find the cockpit voice recorder from the plane, but apparently the device was recorded over, so there is no data to use in their investigation.

Two passenger cell phones that fell out of the plane were also found.

Alaska and United are the two main U.S. air carriers that operate the Boeing 737 Max 9.

United Airlines said it had to cancel about 180 flights Sunday, but managed to get 85 of those flights in the air by switching to other aircrafts.