SAN FRANCISCO – Passengers aboard the ill-fated Asiatic Airways flight described a normal approach that was punctuated by a sudden acceleration of the engines just as they expected the wheels to touch down.

That conformed with the observation of other witnesses who said the plane struggled to reach the end of the runway.

After the landing, flames scorched the red and white jet from its cockpit area to just behind its wings, peeling back the aluminum skin from the top of the aircraft.

Just after the plane crashed, airport tower personnel could be heard talking with the cockpit crew, with a controller saying, “Emergency vehicles are responding. Everyone is on their way.”

The tower also heard from the pilots of a United flight awaiting takeoff, with one pilot saying “We can see people ... and they are alive and walking around.”

A second pilot added: “Between the runways we can see two or three people and they are moving and have survived.”

Witnesses described the tail striking first and then said the plane braked suddenly and spun around. They said the 7-year-old plane did not appear to catch fire until it came to a halt.

“It flipped ... hit the ground,” said one teenage boy who said he was aboard the flight. “The top just totally collapsed on top of a lot of people.”

The boy spoke to reporters outside a holding area for family members and some passengers. Airport personnel whisked the boy away as he talked.

Ben Narasin, a writer who lives south of San Francisco, said he spoke with a pilot who described watching the plane come in “at an exceptionally high rate of descent, not of speed, and the nose was up extremely high.”

“It snapped off the tail ... did not cartwheel ... he didn’t put it down,’’ Narasin added.

Facebook’s Chief Operating Officer Sheryl Sandberg posted a note on her Facebook page that she and three colleagues were originally slated to be on the Asiana flight.

“Taking a minute to be thankful and explain what happened,” she wrote in her Facebook post. “My family, colleagues Debbie Frost, Charlton Gholson and Kelly Hoffman and I were originally going to take the Asiana flight that just crash-landed. We switched to United so we could use miles for my family’s tickets. Our flight was scheduled to come in at the same time, but we were early and landed about 20 minutes before the crash. Our friend Dave was on the Asiana flight and he is fine.”

“Dave” is David Eun, an executive at Samsung who tweeted several pictures from the flight.

“I just crash landed at SFO. Tail ripped off. Most everyone seems fine. I’m ok. Surreal.” Eun tweeted, followed by: “Fire and rescue people all over the place. They’re evacuating the injured. Haven’t felt this way since 9/11.”

Pilots refer to a botched landing of this type as “coming down heavy.”