U.S. military specialists say Israel is clearing the skies of Syrian Migs and wiping out many of the antiaircraft missile batteries in Lebanon through a combination of sophisticated electronic equipment, highly trained pilots and new missiles and jet fighters.

American-built weapons, especially the new F15 and F16 jet fighters and the latest version of the Sidewinder air-to-air missile, are key factors in this deadly duel between the Israeli air force and a Syrian force equipped largely with Soviet-built Mig 21 and Mig 23 fighter planes and mobile SAM6 missiles.

Although some military sources say there are indications that some of Israel's public claims about the numbers of Syrian planes shot down and SAM sites destroyed are exaggerated, there is no dispute that the Israeli air arm has scored overwhelming victories thus far.

But while there is great professional admiration for the military skill of the Israelis, the steamroller quality of their onslaught on the ground and especially in the air has stirred cynicism here at high levels about Israel's continuing demand for more weapons.

"What is most fascinating," one top officer said, "is that the Israeli defense minister, Ariel Sharon, was just through here bemoaning the loss of Israeli advantage and how their edge has been whittled away. It is hard to hold such talks up against the rate of success in this operation."

The results of the current air operations are also certain to be analyzed closely in the Pentagon for another reason. This involves the running battle between those defense specialists at the Pentagon who favor investing heavily in new weapons employing advanced technology and those, especially in Congress, who favor buying more but cheaper weapons.

For the moment, interviews in the Pentagon suggest that the outcome thus far in Lebanon supports the view that the more sophisticated weapons are worth the extra price, but other combat-experienced officers caution that all the results are not in yet.

Indeed, U.S. officials say that the Israelis have made very little information available to Washington about what is going on.

Nevertheless, from whatever information is reaching here from various sources, officials point to the following key factors in the Israeli success in the air thus far.

* Early warning. The location of airfields in Syria is well-known and the distance to the battle area short. Thus the Israelis know the general direction that Syrian planes will come from.

The Israelis are said to be using U.S.-built E2C Hawkeye radar surveillance planes and the radar carried by the F15 fighters to detect the Syrian Migs as they take off. Both planes are reportedly being used as airborne command posts, directing other F15s, F16s and Israeli-built Kfir fighters for quick intercepts and kills. The F15s and F16s are much newer planes than the Mig 21s and Mig 23s.

* Sidewinder missile. By virtually all accounts available here, the star technical performance thus far is being turned in by the new AIM9L Sidewinder missile carried by the F15 and F16.

Unlike earlier Sidewinders that required a pilot to maneuver behind his enemy and fire a heat-seeking missile up his opponent's tailpipe, the new Sidewinder can be fired head-on. This means targets can be hit farther away and that in aerial battles involving scores of planes, as have occurred over Lebanon, an Israeli pilot does not have to get in a position where another Syrian Mig could get on his tail.

The same missile is said to be responsible for many of the victories scored by British Harrier jets in the Falklands war.

* Skilled pilots. "The Israeli pilots are about as good as you are going to get," says one top U.S. officer. "They are the astronauts of their country, incredibly rigidly screened, with a much higher dropout rate than the U.S. Air Force." And, he says, they are always close to the battlefield, have lots of experience and know the region intimately.

* Electronic warfare. The Israelis, U.S. officials say, learned their lessons from the 1973 war when they initially suffered heavy losses from SAMs due to insufficient attention to electronic warfare. The Israelis now have Boeing 707s modified as airborne jammers meant to play havoc with antiaircraft radars. They also have versions of the U.S. "Wild Weasel" electronic system that goes into the cockpit of U.S.-built F4 Phantom jets in the Israeli arsenal. This system helps to deceive SAM radars and guide in missiles that ride down the beam of the enemy radar.

The Israelis have U.S.-built Shrike and Maverick missiles that can be used to attack SAM sites from miles away. For pilots flying in low to duck under the SAM radars and attack the sites with so-called smart bombs, the Israelis also have a cockpit computer system that tells the pilot when to release his bombs.

Sources here say the Israelis are probably using F4s and F16s in the attacks against the SAMs. They also say the short distances mean the Israelis can bring in air strikes from all directions simultaneously against these sites. Israeli and American planes also contain a system that senses when an enemy radar has detected them and sets off a sharp strobe light in the cockpit as a warning.

While reports of Israeli victories in air-to-air combat have come to be anticipated in Middle East wars, perhaps the most remarkable claim by the Israelis thus far is that they have knocked out all 19 SAM6 missile sites without losing an aircraft. The SAM6 is a mobile and extremely lethal missile that can reach out for 25 miles and up to 60,000 feet. These missiles were used with deadly effectiveness by Egyptian forces in the early days of the 1973 war.

On Wednesday, the Israeli command claimed all of these sites had been knocked out, but yesterday they were struck again, suggesting either that more missiles had been brought across the Syrian border at night or that the initial Israeli claims were exaggerated.