Air Force Maj.-Gen. Eitan Ben-Eliahu said Tuesday the cause of the apparent crash was still a mystery and did not rule out that the pilot may have suffered from "spatial disorientation," commonly known as vertigo, during the training mission.

"It is clear that there was something that unfolded at great speed which did not even give them a chance to report back. This could happen from a malfunction, which somehow interfered with their control over the jet and their attempts to overcome it," Ben-Eliahu said.

"A second theoretical possibility is vertigo, which makes one lose control and ultimately led to a crash into the water."

Begin and Harari took off from the Ramat David Air Base in northern Israel at 6:55 p.m. Monday for a training flight with another F-16 off the Lebanese and Israeli coasts. It was Begin's third flight of the day, a routine event.

On their return, about 10 to 20 miles off the coast of Haifa, the pair were to engage in an exercise aimed at detecting and downing a helicopter. Ben-Eliahu said they completed the exercise from an altitude of 4,000 feet, and at 7:42 p.m. asked to perform an additional exercise. At 7:44 p.m. the jet hit the water.

"The last report from the air crew was about 10 to 15 seconds before [the crash] apparently happened, when he asked for more data from the flight controller and then he disappeared from the radar and all communications were lost."

The air force said the weather conditions were good, but it was an exceptionally dark night.