NEWARK, N.J. (AP) -- Investigators were trying to determine why part of a United Airlines jetliner's landing gear failed to deploy, forcing terrified passengers to crouch in their seats and brace for a crash before the pilot touched down safely despite scraping the jet's belly on the runway.
All 48 passengers and five crew members made it off the plane, hustling through its exit doors and sliding down inflated emergency chutes once it came to a stop at Newark Liberty International Airport, one of the nation's busiest airports.
By this morning, the aircraft had been moved from the runway to a hangar. Federal Aviation Administration spokeswoman Arlene Salac said investigators from her agency would inspect the plane and interview the pilots. She said no further information would be released until the investigation is completed -- something that might take weeks or months.
The frightening episode began Sunday morning as Flight 634, from Chicago to Newark, was descending on its runway approach.
Suddenly the plane started rising again and circling the airport, passengers said.
"So we knew something was wrong," said Jim Falk, of Middletown, N.J., who was sitting near the front of the plane.
The captain, who sounded composed, announced over the intercom that there was an issue with some of the landing gear on the Airbus A319, passengers said. Then he told them they'd be landing in three minutes -- and they should gird themselves for a crash, Falk said.
When the aircraft landed, part of its belly struck the runway, United spokeswoman Robin Urbanski said, and part of its right wing was damaged.
But passengers, who cheered and sighed with relief, said the landing seemed controlled, and they praised the skillful pilot, whose name wasn't immediately disclosed.
"If you didn't know they were missing a set of wheels, you wouldn't have thought there was something wrong," said passenger Paul Wasylyszyn, of Chicago.
Another passenger, Paul Lasiuk, also of Chicago, called the landing "unbelievably smooth."
"I've had a lot of worse landings at Newark before," he said.
The passengers were taken by buses to their terminal as the crippled plane, listing to the right, sat on one of the airport's three runways.
The plane's right landing gear didn't extend, though its nose and left landing gear did, the FAA's Salac said.
It wasn't immediately clear what caused the malfunction, said Urbanski, the spokeswoman for Chicago-based United, a subsidiary of UAL Corp. The extent of the damage to the plane's right wing area was being determined, she said.
After the crew reported the problem, the airport was closed for about 20 minutes, said Ron Marsico, a spokesman for the Port Authority of New York and New Jersey, which operates the region's major airports. The airport's other two runways were reopened soon after the plane landed, but some arriving flights were delayed by about an hour.
The plane, which had left Chicago about 6 a.m. local time, remained on the runway late Sunday as investigators inspected it. It was unclear when and how it would be moved.
Sunday's scary landing came a week after a man took advantage of a guard's absence to walk through a security checkpoint exit at the airport and say goodbye to his girlfriend, a security breach that triggered the shutdown of a busy terminal and led to major delays.
Haisong Jiang, of Piscataway, N.J., was arrested Friday and faces a charge of trespassing and a fine of up to $500. He's due in court this week.
A friend of Jiang's, Ning Huang, said Saturday that he's known Jiang for years and that Jiang is "a very good person" who didn't realize the ramifications of his actions.