A DC-9 jetliner with 67 persons aboard circled Baltimore-Washington International Airport for more than an hour last night because of a possible landing gear malfunction, then landed safely at midnight.

The plane, Allegheny Airlines flight 143, was on its landing approach at Norfolk when a warning light and a horn indicated the nose wheel was not properly extended and locked.

The pilot of the twin-jet airliner decided to fly to Baltimore-Washington International because the runway there is longer than the one at Norfolk and Allegheny has maintenance facilities at BWI. The flight originated in Boston and stopped at Philadelphia before flying to Norfolk.

The plane circled the Baltimore field to use up the fuel while the pilot and Allegheny officials on the ground conferred on what course of action to take. At one point the plane made a low pass over the control tower so ground personnel could observe the nose gear.

The wheels were seen to be fully extended, an airline spokesman said, but it was not possible to tell whether they were safely locked.

Ultimately, the spokesman said, the decision was left to the pilot on whether to attempt a normal landing or to bring the plane down on a runway that had been covered with fire-retardant foam. The pilot, who was not identified, chose the conventional landing, the spokesman said, because he thought it would allow him more "maneuverability."

The pilot then made what was described as a "routine landing," touching the plane's rear wheels down first and gliding as far as possible before shifting the load gently to the nose gear. There were no injuries to the 63 passengers and four crew members.

An inspection of the plane later indicated that the front gear had in fact locked and that the malfunction was in the alarm system, an airline spokesman said. Nevertheless, he said, the plane would undergo a thorough examination before it goes back into service.

The passengers, none of whom could be reached for comment, were flown almost immediately after landing to Norfolk on another plane.

The DC-9 is an airline mainstay on short-to-medium-range flights.

Last week, the Federal Aviation Administration ordered stepped up inspection of DC-9 tail assemblies because of reports of cracked bulkheads in the plane's tail assemblies.

Those cracks, which apparently bear no relation to last night's landing gear incident at Baltimore, could lead to sudden loss of cabin pressure, such as was experienced when the tail cone of an Air Canada DC-9 fell off Sept. 17, according to authorities.