Loss of the Sinai Peninsula in a peace agreement with Egypt would be a serious blow to the Israeli Air Force, the vital arm in Israel's basic strategy, according to Israeli military analysis.

Public attention has been focused on the Israeli demand to keep 12 settlements in the Rafia area of northern Sinai, but Israeli generals are said to be far more concerned about retaining control over the three air bases in the Sinai that they have also asked to keep in negotiations with Egypt.

The Israelis say that without Sinai the air force would become vulnerable to attack, considerably reduced in its offensive and defensive capabilities and hard put to compensate for the loss.

The concerns of these military sources reflect the complexity of negotiating a peace agreement satisfying Israel's security needs as well as Egypt's demand that its territory be returned. Leaders of the two countries may be able to agree on broad principles for peace but spelling out the details of the accord is bound to be difficult.

Within Israel proper, to Israeli Air Force is understood to have access only to four airfields, including Ben Gurion International Airport at Lod. In the Sinai, the Israeli Air Force now has access to eight fields, most of which were captured from Egypt in the 1967 war and have been considerably expanded and modernized.

A large part of the problem is that the Israeli Air Force today is radically different from what it was a decade ago when it wiped out the Arab air forces in a series of surprise strikes that caught the planes on the ground. Israel's air force has more than triple the number of planes it had 1967. A growth that was largely possible because of the availability of the wide open spaces of the Sinai. Now, the Israeli Air Force is being asked to return to a small area the size of New Jersey or Massachusetts.

The Arab air forces, meanwhile, have not only grown, but they have also learned the lessons of dispersal and readiness taught them by Israel in 1967.

The nightmare of Israeli Air Force generals is a "1967 in reverse," - the fear the Arab air forces could, if they took the initiative, deal to Israeli airpower the same kind of death blow that the small Israeli air force dealt the Arabs by exploiting the element of surprise in 1967.

The Israelis say they are now confident that they would have enough warning so that their planes would not be caught on the ground, but that a concentrated air offensive against the runways of the few airfields inside pre-1967 Israel could have the same effect as a surprise attack. The Israeli Air Force would have no landing places to return to.

Israeli military experts note that even if the Egyptian air force were to stay out of a war, there are more than a thousand Arab combat aircraft on the "eastern front" of Syria, Iraq, Jordan and Saudi Arabia.

That number of planes concentrating on four sets of targets would have a good chance of knocking out the air fields, even against a heavy aerial defense. Syria and Iraq, both of which are in the "rejection front" that spurns Egypt's peace moves, have about 800 planes.

Defense Minister Ezer Weizman, the commander of the Israeli air force who prepared it for the 1967 war, is understood to have offered Egyptian President Anwar Sadat part of Israel's Negev Desert in exchange for the Rafiah area in northern Sinai and the Etzion air field south of the port of Eilat.

Authoritative sources say Sadat would not hear of it, saying that the Sinai had been part of Egypt "for 3,000 years," and that he would not be the Egyptian leader to give up any of it. The Israelis counter that the Sinai Desert was only made part of the Egyptian province of the Ottoman Empire in 1906.

The Israeli idea is to move the long north-south frontier between the Negev and Sinai eastward for two or three kilometres to give Egypt enough square yardage to compensate it territorially for the loss of Rafiah and Etzion, an area the Israelis say constitutes 2 per cent of the Sinai's total land.

Some American officials are understood to feel that this is not unreasonable, but they say that Sadat is simply in no mood to entertain any such idea. Under the circumstances, some Americans say Israel should be thinking about building more airfields inside its 1967 borders.

Israeli analysts say there are simply not enough facilities inside Israel to handle the number of planes Israel has now - more than three times the 1967 operational combat planes with which Israel went to war in 1967. They add that there are not enough hours in the day or night to schedule adequate training for all the pilots in the limited air space that would be available.

Faced with a similar problem, West Germany's Luftwaffe ships hundreds of pilots yearly to train over the open deserts of Arizona.

In his memories, "On Eagles's Wings," Weizman speaks of his bitterness in 1957, when Israel had to return the Sinai to Egypt after an earlier war. He describes making a last pass over El Arish, the Sinai's largest city, in a Piper Cub.

"Some evil instinct made me fly very low, between the palm trees, zooming over houses and courtyards, with a terrible anger in my heart. I almost shouted, 'We'll be back! Remember, we'll be back!'"

In the military negotiations in Cairo, Weizman, the chief Israeli military negotiator, had demanded continued control of three fields:

Eitam in the Rafiah area of northern Sinai.

Ofira at Sharm el Sheikh, an Egyptian base that the Israelis have greatly improved. That base gives Israel the offensive capability of controlling the Red Sea all the way to the Bab el Mandeb strait at the eastern entrance between Aden and Djibouti.

Etzion, just south of the exposed Israeli port of Eilat at the head of the Gulf of Aqaba. Israeli officials make it clear that they regard this as by far their most important air base in Sinai, one that is well worth a diplomatic crisis.

The Israelis say they are resigned to returning the giant air base of Bir Gafgafa (called Refidim by Israel) in central Sinai and four other smaller fields. They have already returned two fields to Egytp under the second Sinai disengagement agreement.

The distinct impression one gets from the Israelis is that their demand for the bases near Rafiah and Sharm el Sheikh are bargaining chips, but that they are absolutely determined to have Etzion near Eilat.

Not only would it be Israel's southernmost air field and give it control over the Strait of Tiran, the bottleneck between the Gulf of Aqaba and the Red Sea, but the Israelis say it would provide what they view as absolutely essential security for the growing port of Eilat - the narrow apex of Israeli territory at the head of the Gulf of Aqaba. Without the base there, the Israelis argue, the port is exposed to gunfire from three neighboring Arab states - Jordan, Egypt and Saudi Arabia.

The Israelis talk about the tremendous cost of reconstructing inside Israel even a fraction of the air force's infrastructure in Sinai. One estimate is that moving the Etzion base north would cost about $1 billion.

Some Israeli sources have already suggested that the United States foot the bill for relocating Israeli military facilities. It would surprise nobody in Israel if Weizman raises this issue during his forthcoming mission to Washington to seek nearly 200 advanced U.S. warplanes.

While there, he will undoubtedly explain the new problems of the Israeli Air Force, an organization that is in a position to argue with conviction that it is a perfect expression of the late Israeli Prime Minister Levi Eshkol's classic advice to his negotiators on their bargaining posture toward to United States. Depict Israel, he said, as "Samson the weakling."