(NewsNation) — Alaska Airlines has begun preliminary inspections on some of its Boeing 737-9 Max aircrafts this weekend, saying up to 20 planes could undergo inspection.

The carrier also said it would initiate and enhance its own layers of quality control to the production of the airplane and has initiated a review of Boeing’s production quality and control systems, including Boeing’s production vendor oversight.

This comes after a terrifying incident last week when a door plug blew out of one of its planes, forcing an emergency landing.

After the incident, the Federal Aviation Association grounded 171 Boeing 737 Max 9s and opened an investigation into the company.

The grounded planes were slated to return to the runways Sunday but both United and Alaska Airlines pushed it back to Wednesday, pending FAA approval.

Alaska Airlines said that it engaged in a candid conversation with Boeing’s CEO and leadership team earlier in the week to discuss their quality improvement plans to ensure the delivery of the highest quality aircraft off the production line for Alaska.

FAA administrator Mike Whitaker said the agency is requiring plug door inspections of select 737 Max 9s, wanting more data before approving Boeing’s inspection and maintenance process.

“This administrator is taking a very methodical and data-driven approach to these inspections. They’re going to be looking at data. They’re going to be looking at this methodically and making sure that all those inspections are going to be carried out properly, and that the airplanes are not going to fly until the FAA is happy with the entire process,” said Dr. Hassan Shahidi, president and CEO of the Flight Safety Foundation.

Over 200 United and Alaska Airlines flights have been canceled each day this week due to the FAA-mandated grounding.

So far, both airlines have found loose parts on the 737 Max 9s after technicians completed initial checks.

Reuters contributed to this story.