A MILESTONE FOR NATO : 20 Minutes Over Bosnia

The West’s minute-by-minute entry into the Balkans war, according to NATO:

* 6:31 a.m. Bosnia time: An Advance Warning and Control Systems (AWACS) plane sounds the alarm at dawn. NATO aircraft report six jets flying five nautical miles southward from Banja Luka.

* 6:35: The AWACS pilot orders the jets to land or depart the “no-fly” area. At the same time, he calls in the cavalry: a pair of U.S. Air Force F-16s on routine patrol farther south.

* 6:42: The fast-approaching fighters issue the same warning: Get out or face attack.

* 6:43: In the critical next minute, two things happen almost simultaneously. The F-16 pilots see the Serbian jets make what appears to be a bombing run and see what seem to be explosions. Just then, the American pilots, based at Aviano in northern Italy, receive permission to engage from NATO commander.

* 6:45: Lead plane fires an AIM 120 active radar missile, destroying one of the Serbian planes.

* 6:47: The same NATO jet destroys a second Serbian plane with a short-range heat-seeking Sidewinder missile.

* 6:48: The same F-16 shoots down a third plane, also with a Sidewinder. Two other American fighters arrive.

* 6:50: The lead plane of the pair destroys a fourth plane with a Sidewinder. By now, the surviving two Serbian planes are fleeing. They are not pursued. Radar indicates that they fly westward at first, then north and east toward Croatia. They apparently land in or near Banja Luka. American jets were not fired upon. Monday night, American officials in Naples said the hat-trick American pilot would be identified only after he had been debriefed in the next day or two.