What Caused NJ Airplane's Landing Gear to Fail?

NEWARK, N.J. --

Investigators are trying to determine why part of a United Airlines jetliner's landing gear failed to deploy as it approached New Jersey's Newark Liberty International Airport.

The malfunction forced terrified passengers to crouch in their seats and brace for a crash before the pilot touched down safely Sunday despite scraping the jet's belly on the runway.

All 48 passengers and five crew members made it off the plane from Chicago.

Passengers cheered when the plane landed. They say the landing was smooth.

Federal Aviation Administration spokeswoman Arlene Salac says the plane's right landing gear didn't extend, though its nose and left landing gear did.

United spokeswoman Robin Urbanski says the extent of the damage to the plane's right wing area is being determined.

The emergency landing closed the airport for about 20 minutes and caused flight delays.