A People Express Airlines Boeing 737 jetliner returned to Dulles International Airport shortly after takeoff early yesterday when a passenger reported seeing something fall from the engine, according to spokesmen for the airline and the Federal Aviation Administration.

The 7 a.m. flight to Newark Airport, with 114 people aboard, was about 10 miles northeast of Dulles when a passenger saw a cowling -- a metal collar two feet wide, six feet in diameter and weighing about 20 to 40 pounds -- fall from one of the plane's two engines, said Russell Marchetta, a spokesman for the airline.

Passengers said they felt a slight shudder, but no one was injured and the plane returned safely to Dulles, Marchetta said. The passengers on Flight 183 left Dulles on another plane about noon, he added.

One passenger, who declined to give his name, said he and several other passengers gave up waiting for the later flight and left the airport.

"We were only about 10 minutes out of Dulles when I felt the plane shudder as though it was passing through some turbulence," said the passenger. "Then I saw another passenger hail the stewardess, who in turn came back with the copilot, who looked out the window. I knew something was wrong by the way the stewardess and the copilot were talking up near the cockpit."

Shortly thereafter, the passenger said, there was an announcement that the plane was returning to Dulles because of a problem. The passengers remained calm, he said.

Marchetta termed the incident an "unusual occurrence."

"We will try and find out why it wasn't detected earlier," Marchetta said. "It might be metal fatigue. We just don't know at this point. This is the first time this has happened to us."

Federal Aviation Administration spokesman David Hess said the cowling problem with the People Express Boeing 737 was not related to the engine problems that caused a Boeing 737 to explode and burn in Manchester, England, on Aug. 22, killing 54 people.

"There was no danger to the passengers when the cowling fell off," Hess said. "The cowling protects the engine, suppresses noise and streamlines the airflow. The captain could have shut off that engine and still flown safely back to the airport."

Hess said that a National Transportation Safety Board inspector examined the plane yesterday afternoon and released it to return to Newark for repairs. He said FAA flight standards inspectors were scheduled to investigate the incident. The missing piece has not been recovered, Hess said.