But many of the Alaska Airlines passengers arriving at SFO from Austin didn't know they were flying on a Max 9, like Windy Chian, who lives in San Francisco.
"I'm so glad I didn't know," Chian said with a laugh. "I probably would have flown anyway, but I would have researched it more."
U.S. regulators grounded all Max 9s immediately after a panel broke off an Alaska Airlines flight on January 5. According to the Associated Press, Alaska and United Airlines both resumed flying their Max 9s on Friday. They are the only U.S. airlines that currently operate the Max 9.
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"It's not a software problem. It's not a design problem with the airplane. It involves making sure that four bolts were put into the door and properly tightened. It's not hard," said ABC News Analyst Steve Ganyard.
The FAA has been inspecting all Max 9 planes. It is also investigating if Boeing and its suppliers followed necessary manufacturing safety procedures. Any violations could lead to sanctions.
Despite the inspections, some passengers -- like Fremont resident, Amber Engle -- say they're still apprehensive.
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"I think it's important that they are inspected, but I am assuming they had been inspected before as well. So, there is a little bit of self-responsibility, too. Trying to be mindful of your own safety," said Engle, who is a loyal Alaska Airlines passeneger.
Meanwhile, U.S. airline officials and aviation regulators point out that despite some close calls, there have been no fatal crashes of a U.S. airliner since 2009.