An Air Force U-2 spy plane returning from a nine-hour reconnaissance mission over Afghanistan crashed in predawn darkness yesterday in the United Arab Emirates, and the pilot died, military officials said.

The cause of the crash could not be immediately determined, the officials said. But a senior military officer familiar with preliminary internal reports said there were no indications of hostile fire.

The officer also said that before the plane went down, there were no communications of trouble from the pilot, who belonged to the 380th Air Expeditionary Wing and had long experience flying U-2s. The name of the pilot was not released.

The U-2 is a single-seat aircraft that can cruise at more than 70,000 feet, twice the normal altitude of commercial airliners. In use frequently over Afghanistan and Iraq, the plane and its missions have tended to be cloaked in secrecy.

Even mention of the base it uses in the Middle East -- the UAE's Al Dhafra Air Base -- has frequently been avoided by U.S. military and diplomatic authorities, citing host nation sensitivities, although the fact is widely known.

The UAE's news agency WAM said the U-2 crashed while trying to land and that UAE authorities were assisting in a U.S.-led investigation. The agency said the United States has an agreement with the UAE that allows use of some military facilities.

A veteran of the Cold War with the former Soviet Union, the U-2, which was first flown in 1955, has proven itself very reliable. But aviation experts say it can be difficult to fly because of unusual landing characteristics and because its high-altitude missions require pilots to wear bulky full-pressure suits.

The existence of the U-2 first became public in 1960 when one flown by Francis Gary Powers for the Central Intelligence Agency was shot down over the Soviet Union. After parachuting to safety, Powers was captured and later convicted as a spy. He was held for almost two years before being traded for a KGB captive.

Another U-2 was shot down over Cuba during the missile crisis in 1962, and others have crashed from time to time, although yesterday's was the first reported U-2 loss during the Afghanistan and Iraq conflicts.

The pilot of a U-2 spy plane like this one was killed in a crash after a nine-hour mission over Afghanistan.