Trans World Airlines officials said yesterday that they are working through diplomatic and other channels to reclaim the jetliner seized by hijackers June 14 en route from Athens to Rome. The plane has been sitting at the Beirut airport since June 16.

"We want it back and we intend to get it back," TWA spokesman Jerry Cosley said. "But much like the release of the hostages themselves, we think the environment there is delicate, and we are working through discreet diplomatic and other channels to determine the aircraft's condition and get it out of there as quickly as possible."

The plane is a Boeing 727-200, a three-engine medium-range jet with seats for 145 passengers. TWA owns the plane and values it at $9 million to $10 million. At the time it was seized, it was used to shuttle passengers from Cairo to Athens to Rome and back. In Rome, passengers transferred to bigger planes for transatlantic flights.

TWA's efforts have been complicated by the U.S. government's attempts to isolate Beirut airport and ban flights to the United States by Middle East Airlines, the Lebanese carrier. Under normal circumstances, TWA would ask MEA, as the host carrier, to provide maintenance support for the jetliner and perhaps even a flight crew, but that approach is not available.

"It's unlikely you would see a TWA or an American crew in Beirut," an airline official said, adding that TWA has been checking with other international airlines to see if a flight crew might be available. Another source said a Syrian crew was considered a possibility, but that could not be confirmed.

Despite those uncertainties, "I think there is a very reasonable possibility that we'll get it back," the official said.

TWA officials believe that the plane is capable of flying safely. They base their belief partly on the debriefings of three cockpit crew members who were held captive on the aircraft until just before their release, with the remaining hostages, June 30.

The plane's engines were run to provide air conditioning and electricity while the crew was kept on board. All three engines are believed to be in good operating condition.

The passenger cabin is another matter. It was "trashed" during the hijacking and the events following, officials said. However, recent press photographs have shown cleaning crews on the plane, so "we don't know what the situation is," an official said.

The plane has remained under guard but officials are uncertain who controls the guards.

If the plane is recovered, the plan is to fly it to a nearby airport, inspect it and then fly it to the TWA maintenance base in Kansas City for an inch-by-inch check. The plane was within 30 days of an annual maintenance check at the time of the hijacking.