There is no word so far on any casualties. The aircraft - operated by the South Korean airline Asiana - is on the runway, with plumes of smoke rising from it.
Firefighters and rescue teams are at the scene.
Updated:CalFire confirms 303 passengers on board, all accounted for. They're also reporting no fatalities, one passenger in critical condition, others with varying degrees of injury.
A passenger on the airplane sent out a tweet and a photo shortly after reports of the crash appeared on Twitter:
I just crash landed at SFO. Tail ripped off. Most everyone seems fine. I'm ok. Surreal... (at @flySFO) [pic] — https://t.co/E6Ur1XEfa4
— David Eun (@Eunner) July 6, 2013
This YouTube video was shot just after the crash:
Update 2:
Conflicting reports on casualties. KVTU is reporting two deaths, but I haven't been able to get confirmation. Here's the recording from the tower:
