Officials have recovered a part of an Alaska Airlines Boeing 737 Max passenger jet that blew off during a flight from Portland, Oregon to Ontario, California on Friday.
The plane was minutes into the flight and was able to return to the Portland airport. All 171 people and six crew members were unharmed in the incident.
The U.S. Federal Aviation Administration (FAA) ordered that all 737 MAX aircraft be grounded on Saturday. The emergency order affected all 737 MAX 9 planes around the world.
Reports say the part that failed was called a panel or "door plug." U.S. National Transportation Safety Board Chair Jennifer Homendy said a schoolteacher found the part in a Portland neighborhood on Sunday.
The investigation into the incident is likely to last months.
What part failed?
The 737 MAX 9 aircraft has several different designs. One can seat more than 200 passengers. This version needs to have two extra exits to meet safety rules which require all passengers to be able to escape the aircraft in 90 seconds in case of an emergency.
However, the Alaska Airlines plane has fewer than 180 seats. This version of the 737 MAX 9 is not required to have the extra exits. As a result, the plane has a panel, or permanent door plug, over the area on the plane's body that would normally have a door. Some other versions of Boeing 737s also have door plugs.
The Associated Press reports that a company called Spirit AeroSystems installed door plugs on 737 MAX 9s, including the Alaska Airlines plane.
What are airlines doing?
Alaska Airlines has grounded all 65 of its 737 MAX 9 aircraft. They are to be inspected and to undergo maintenance. Some of the planes were still in service on Saturday, but they were grounded after the FAA ordered all operators of MAX 9s to carry out inspections.
Alaska Airlines said it canceled 170 flights on Sunday. By early Monday, 20 percent of the carrier's flights were canceled, the AP reported.
United Airlines is the world's biggest operator of MAX 9 planes. It grounded all 79 of its planes. The two airlines are the only U.S. passenger airlines that operate the planes.
The AP says six other airlines also operate the Boeing aircraft. There are 215 of the planes in service around the world.
Air travel safety
U.S. officials have noted that air travel remains very safe. There has not been a deadly crash of a U.S. airliner since 2009. However, the FAA held a big safety meeting last year after a series of incidents.
The Alaska Airlines incident again brought attention to the 737 MAX aircraft. Aviation officials grounded MAX 8 aircraft around the world for nearly two years after crashes in 2018 and 2019. The 737 MAX 8 is a little smaller than the MAX 9.
Anthony Brickhouse is a professor of aviation safety at Embry-Riddle Aeronautical University in Florida. He said it is too soon to know if the incident is the result of a problem with the MAX 9. He said government officials and airlines will confirm that the planes are safe before returning them to service.
"When passengers board a flight, they should feel confident that the aircraft they are flying on is safe," Brickhouse said.
After the accident, Boeing released a statement saying it regretted the effects "this event has had on our customers and their passengers."
It said it supported the FAA's decision and was assisting investigators.
I'm Mario Ritter Jr.
Mario Ritter adapted this story for VOA Learning English from Associated Press and Reuters sources.
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component –n. a part of a system or a machine
install –v. to put something in a machine in place so that it can be used correctly
maintenance –n. to keep something such as a machine in good working condition
regret –v. to wish something did not happen; to feel sorry that something was done