Pentagon spokesmen insisted yesterday that the Mediterranean exercise that precipitated an attack on two Navy jet fighters was just another routine drill -- "like a skeet shoot," as one said -- even if the location was somewhat unusual.

Official sources said, however, that the decision to hold the maneuvers in waters that Libya has claimed since 1973 was reached by the National Security Council, not the chief of naval operations.

The area in question is called the Gulf of Sidra, which cuts from the Mediterranean into the Libyan shore for about the center third of the country. In 1973, Libya claimed that its national waters include all of the gulf below 32 degrees, 30 minutes north latitude, a line about 200 miles north of the southernmost tip of the gulf.

The United States has never recognized that claim, the Pentagon said yesterday, and legally recognizes a line three miles offshore. However, the Pentagon said, it respects a line 12 miles from the shore, although it does not legally recognize it.

Navy maneuvers have been conducted within the 32-degree, 30-minute line four times in the past seven years, the Pentagon said, although the last time was more than two years ago, in July 1979.

The maneuver that created this flap was described by the Pentagon as a "missile-firing exercise." It involved two carrier battle groups totaling 16 ships: the carriers Nimitz and Forrestal, each escorted by two cruisers, two frigates, two destroyers and one destroyer escort. Each carrier has about 100 aircraft, including a large number of F14s. Two ships, neither of them carriers, were south of the 32-30 line at the time of the incident.

The area of the exercise, in the southern Mediterranean, was chosen because it does not interfere with major shipping lanes, the Pentagon said, and is ideally suited for a large-scale exercise. Public notification to mariners and airmen that the maneuvers would take place was sent out days ago, and the "danger area" was defined. If a non-Navy ship were to penetrate the danger area during the exercise, "we would have to delay" it, a Pentagon spokesman said.

"What happens," a spokesman said, "is that one ship gets on one side of the area and shoots a pilotless airplane -- a drone-- across the range. Ships located on the other side of range, or airplanes launched from the carriers, shoot certain types of missiles at the drones." The aircraft from the two carriers flew "hundreds" of sorties. A sortie is a single mission or attack by a plane.

Aircraft also flew reconnaissance missions "to make sure no other aircraft strayed into the corridor," a spokesman said, and it was two of these aircraft that encountered the Libyan jets.