Chicago, Jan 9 : United Airlines said Monday that it has found loose bolts during inspections of its 737 Max 9 fleet in the wake of a door plug getting blown out of an Alaska Airlines plane over the weekend.

"Any findings will be fully addressed in a matter that satisfies our safety standards and FAA compliance," Alaska Airlines said.

"The safety of these aircraft is our priority and we will take the time and steps necessary to ensure their airworthiness, in close partnership with the FAA," the airline added.

United won't say how many planes had loose bolts.

"Since we began preliminary inspections on Saturday, we have found instances that appear to relate to installation issues in the door plug -- for example, bolts that needed additional tightening," United said in a statement. "These findings will be remedied by our Tech Ops team to safely return the aircraft to service."

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The Federal Aviation Administration grounded all 737 Max 9s in the wake of the Alaska Airlines incident.

"The FAA’s first priority is keeping the flying public safe," it said in a statement. "We have grounded the affected airplanes, and they will remain grounded until the FAA is satisfied that they are safe."

United said that due to the emergency inspections, it had to cancel 200 Max 9 flights on Monday and expects "significant cancellations" on Tuesday, as well.