The pilot of a All Nippon Airways jumbo jet carrying 517 passengers and crew was stabbed to death in flight Friday by a hijacker who demanded that the plane be diverted to a U.S. air base north of Tokyo.

Police said that after stabbing the pilot with a eight-inch knife, the hijacker briefly sat in the copilot's seat and took the plane's controls. He was then overpowered by the copilot and six passengers as the plane rapidly descended to an altitude of about 1,000 feet near Yokota Air Base. The plane returned safely to Haneda Airport near downtown Tokyo and no passengers were injured.

Japanese media reported that an off-duty ANA pilot traveling as a passenger first took control of the Boeing 747 during the struggle and stopped its steep dive; the copilot then landed the plane.

It was unclear today why the hijacker wanted to go to the large American air base, which has been the subject of controversy recently because the newly elected governor of Tokyo has demanded its closure and return to Japanese control.

Police said the hijacker, a 28-year-old Tokyo resident, may have psychiatric problems. He told investigators he likes flight simulation games and wanted to fly a real airplane.

Prime Minister Keizo Obuchi offered his sympathy to the family of pilot Naoyuki Nagashima, 51, a 29-year veteran of the airline and the first crew member ever killed in a domestic hijacking in Japan. Obuchi also promised an investigation about how the hijacker was able to smuggle such a large knife through security at Japan's largest domestic airport. The Ministry of Transport immediately heightened security at all Japanese airports.

Police said the man confronted a flight attendant shortly after the plane took off at 11:23 a.m. Friday (10:23 p.m. Thursday EDT), bound for Sapporo on the northern island of Hokkaido. He reportedly threatened the woman with his knife and forced his way into the cockpit, where he forced the copilot out into the cabin and demanded that the flight go to Yokota and to Oshima island off the Tokyo coast. There were unconfirmed reports that the man also wanted the pilot to fly under the Rainbow Bridge, the spectacular span that crosses Tokyo Bay not far from Haneda Airport.

Yoshiko Kawase, 60, told reporters that she had been sitting in the plane's fifth row, near the hijacker, whom she described as wearing soiled white gloves. She said he stood up and started screaming "Go! Go!" at the flight attendants, moving them toward the cockpit.

An unidentified passenger told reporters he was sitting near the front of the plane's upper deck, where the door to the cockpit is located, when the hijacker threatened the flight attendant with his knife and said, "Take me to the captain if you don't want to die."

Transport Ministry officials said radio transmissions from the plane were normal for almost 20 minutes after the plane took off, then air traffic controllers heard the hijacker's voice giving instructions to the pilot. Those instructions were apparently followed until the hijacker stabbed the pilot in the neck after trying to tape his mouth shut.

The hijacker reportedly then sat down in the copilot's seat and began fumbling with the controls in an attempt to fly the plane. As the plane dived, the copilot and six other people forced their way back into the cockpit and subdued the hijacker.

The hijacking was Japan's 17th since 1970.