The front landing gear of a flight arriving at New York's LaGuardia Airport collapsed on Monday immediately after the plane touched down on the runway.
Officials said the air craft went skidding before coming to a halt on the runway.
Ten passengers were treated at the scene and six were taken to a hospital with minor injuries, Thomas Bosco, acting director of Aviation for the Port Authority of New York and New Jersey said, which oversees the area airports. The six crew members were taken to another hospital for observation.
There was believed to be 150 people on board Flight 345 coming from Nashville, Tennessee, according to Dallas-based Southwest.
Bosco said the nose gear of the plane collapsed when it landed at 5.40pm, and “the aircraft skidded down the runway on its nose and then veered off and came to rest in the grass area.”
There was no advance warning of any possible problem before the landing, he added.
Passenger Anniebell Hanna, 43, said the flight had been delayed leaving Nashville. Passengers had heard an announcement saying “something was wrong with a tire,” she said, waiting in a room at LaGuardia several hours after the incident.
At LaGuardia, “when we got ready to land, we nosedived,” said Hanna, a sergeant first class with the South Carolina National Guard. She and some family members were coming to New York for a visit.
“I hit my head against the seat in front of me,” she said. “I hit hard.”
Emergency crews were seen spraying foam toward the front end of the plane on the tarmac. The Port Authority said the passengers exited the plane by using emergency chutes.
The airport was temporarily closed, but one of two runways was operating shortly after 7pm, and Bosco said the Port Authority was hoping to have the airport fully open by Tuesday morning.
The Federal Aviation Administration and the National Transportation Safety Board are investigating.
Richard Strauss, who was on a nearby plane waiting to depart for Washington, said the nose of the plane was “completely down on the ground. It's something that I've never seen before. It's bizarre.”
A rear stairwell or slide could be seen extending from the Southwest aircraft, said Strauss, who owns a Washington public relations firm. His plane, which was about 100 yards (90 meters) from the Southwest flight, wasn't allowed to taxi back to the gate, he said.
Bobby Abtahi, an attorney trying to catch a flight to Dallas, was watching from the terminal and heard a crowd reacting to the accident.
“I heard some people gasp and scream. I looked over and saw sparks flying at the front of the plane,” he said.
The incident came 16 days after Asiana Flight 214 crash-landed at San Francisco's international airport on 6 July, killing two Chinese teenagers; a third was killed when a fire truck ran over her while responding to the crash, authorities said. Dozens of people were injured in that landing, which involved a Boeing 777 flying from South Korea.
Additional reporting by agencies