Grounded American Airlines Boeing 737 Max 8 lands at San Francisco International Airport

SAN FRANCISCO (KGO) -- Boeing's 737 Max aircraft were grounded by the United States on Wednesday, but apparently some are still flying.

Sky7 was over San Francisco International Airport as one of the planes came in for landing on at about noon on Friday.

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The plane belonged to American Airlines and after touching down it sat on the runway for about 20 minutes. It then was towed near one of the hangars and no passengers got off.

It is not clear where the airplane flew in from and why American Airlines chose to send it to San Francisco International Airport.

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Since October two Boeing 737 Max 8 aircraft have crashed killing everyone on board. The most recent involved a plane that had just taken off from an airport in Ethiopia.

American, United and Southwest Airlines are the only carriers in the United States that fly the planes