The Federal Aviation Administration said that they will require "immediate inspections of certain Boeing 737 Max 9 planes" after the window on one such plane blew out mid-flight on Friday. 

The FAA's statement, released on Saturday afternoon, said an "Emergency Airworthiness Directive" would be released shortly as well. These directives are issued "when an unsafe condition exists that requires immediate action by an owner/operator," according to the agency. 

This will affect about 171 planes worldwide, the FAA said. Safety inspections for each plane will take between four and eight hours. There have been about 218 such planes delivered around the world, the FAA said, but not all such aircraft were in operation at the time the EAD was issued. 

"Safety will continue to drive our decision-making as we assist the NTSB's investigation into Alaska Airlines Flight 1282," FAA Administrator Mike Whitaker said. 

The moves come after a window on one of the plane models detached mid-flight, forcing the plane to make an emergency landing just minutes into its trip from Portland, Oregon to Ontario, California. There was no one in the seats next to the window, and no serious injuries were reported among the plane's 174 passengers or six crew members. 

"All of a sudden I heard, like, a big bang. I didn't know exactly what was going on," one woman aboard the flight told CBS News. "I look up and the oxygen masks were hanging from the ceiling and then I look to my left and there's this huge chunk, part of the airplane just missing. The wind is just extremely loud, there's wind blowing everywhere."

Alaska Airlines said on Friday that they would ground all 65 of their Boeing Max 9 aircraft. 

"Each aircraft will be returned to service only after completion of full maintenance and safety inspections," the airline said. On Saturday morning, the airline said that inspections on more than a quarter of the fleet had been completed, with "no concerning findings." Aircraft will be returned to service after they are inspected, the airline said. 

Alaska Airlines said on Saturday that guests whose flights had been impacted by the groundings could rebook their travel or request a refund.

"We deeply apologize to our guests whose flights have been impacted," the airline said.

CBS News previously reported that the Boeing 737 Max 9 aircraft had been delivered to the airline in October. In the United States, only Alaska Airlines and United Airlines use the aircraft. United has about 80 of the planes, but it's not clear how many were operating at the time of the Alaska Airlines incident. 

In:
• Federal Aviation Administration
• Boeing
• Alaska Airlines
• Boeing 737 Max
• Oregon
• California