The teen - a USA citizen - was traveling alone and appeared to be in emotional distress during the flight, Yakel said.
No runways or other flights were affected, Yakel said. "The door's open. Someone jumped off, '" said Matt Crowder of Atherton, California.
"I heard the plane land and the door open nearly at the same time and then I saw someone.it was as if he was flying out", said passenger Sarah Gibson.
That's it. Luckily we just landed on the tarmac and everybody was like, 'the emergency door's open, ' and they're like, 'something happened, ' " said witness Anielka Ruiz.More news: Manufacturing PMI at 47.9, records steepest contraction since February '09
More news: Abu Dujana not involved in many attacks, was a nuisance: Army
More news: Google's keyboard app for iPhone adds helpful new features
'It was as if he was like flying out, like it was really fast, ' passenger Sophia Gibson told San Jose television station KNTV.
A passenger has opened an aeroplane door and jumped out prior to the plane arriving at the terminal in San Francisco. The teen will also be transported to a hospital for psychiatric evaluation.
The airline says it is cooperating with authorities in the ongoing investigation. Other passengers said he seemed anxious and fidgety during the flight and that he acted very quickly, making it hard for anyone to stop him.
However, passenger Isaac Rodrigues told the Los Angeles Times that a flight attendant had to block the opening with her body as there was no door to close after the teen had jumped.
"People were yelling, 'Tell the flight attendants".