Although the Begin cabinet says the sale of U.S. planes to Egypt and Saudi Arabia "constitutes a threat to the security of Israel," this battle-tested country is already adjusting to it. What is more painful, though, is adjusting to the dismaying possibility that the long-time U.S.-Israeli "special relationship" may not in the future be quite as special as in the past.

Other American presidents have from time to time toyed with the idea of a so-called "even-handed" policy toward the Middle East, but the plane package is the first time it has actually been practiced in a tangible way. It is deeply distressing to the Israelis, for they simply can't understand how, in American eyes, they could be equated with Arab nations that have for so long been hostile to the United States as well as Israel.

The sense of hurt is widespread because the Isaelis justifiably see themselves as America's only steadfast and dependable ally in the Mideast. They think, also with good reason, they have contributed to America's security, too.

Only a few days before the Senate voted for the plane deal, Yigal Allon, the former Israeli foreign minister, told a group of Americans attending the dedication of the Truman Memorial Institute at Hebrew University that he personally had "frequently heard American presidents, secretaries of state, and senators of both parties express their belief in the importance of Israel to American national interests."

Major Gen. George Keegan, visiting Israel after retiring as U.S. Air Force chief of intelligence, put it more strongly. "I can say without reservation," he told The Jerusalem Post, "that for every dollar of support which America has given Israel, we have gotten a thousand dollars worth of benefits in return, which are incalculable in their value to the U.S. armed forces."

The U.S. government, Keegan added, "does not seem to perceive what to me, as an American, is the single most essential fact of life about Israel in the Middle East, and that is that Israel is the single key to balancing Soviet imperialism in the Mediterranean."

The polite, but persistent, question that visiting Americans get here is: How can the United States "lump" Israel indiscriminately with Saudi Arabia, which struck America the worst economic blow in its history, and with Egypt, which for so many years collaborated with Russia and broke relations with Washington?

The Saudi reference, of course, was to the oil embargo against the United States at the time of the 1973 Yom Kippur war, followed by the abrupt 500 percent increase in the price of oil, which ruthlessly drove up the cost of living in the United States and depressed the dollar.

It was President Anwar Sadat of Egypt who, equipped with Soviet arms, launched the Yom Kippur war, which, at its climax, culminated in a confrontation that Richard Nixon says was "the most serious threat since the Cuban missile crisis" of 1962.

It is hardly surprising, then, that Israelis do not share President Carter's view that Sadat is the "world's foremost peacemaker." Nor do they understand how the Carter administration can look upon the ruling family of Saudi Arabia as "moderate," "benign," "cooperative" or, in Carter's own words, "highly responsible in every action they've taken."

To the Israelis this sounds like a case of mistaken identity. They look on the Arab oil gouge of the United States as blackmail and extortion. They regard the momentarily stabilized price ceiling as reflecting not moderation, but an oil glut so huge that it threatens the future of the cartel.

Several weeks ago, when the administration was assuring Congress that Saudi Arabia would never use U.S. arms against Israel, Crown Prince Fahd was saying, "Saudi Arabia allocates all its forces and strength to bring about victory of the Arab rights . . . This means that the task entrusted to our army is not only to protect the kingdom, but that it could intervene anywhere that our national duty commands."

Just before that Prince Sultan, the Saudi defense minister, said, "All we own is at the disposal of the Arab nation, and will be used in battle against the common enemy." Meanwhile, the Saudis continue to send the Palestine Liberation Organization $40 million a year, along with compliments for its most recent terrorist raid on Israel.

As for Sadat, the Israelis are not surprised at Carter's crush on him, for they have seen the Egyptian president beguile many other leaders, including Libya's Muammar Qadaffi, Syria's Hefez Assad and the PLO's Yasser Arafat, none of whom is speaking to him today.

In his time, Sadat has collaborated not only with the communists but with Nazis and Nasserite socialists. In the end, he jilted all of them. Many old hands here would bet that sooner or later Carter will be next if he is unable to deliver what Sadat is looking for.

In the long run, Carter may come to realize that he was right the first time when, on Sept. 29, 1976, at Plains, he said he was opposed to supplying weapons to Egypt, Jordan or Saudi Arabia. In that campaign statement he said:

"It's not possible to encourage both Arab moderation and Arab militarism at the same time . . . I'm concerned with the way in which our country, as well as the Soviet Union, Britain and France, have poured arms into certain Arab countries far beyond their legitimate needs for defense and five or six times more than Israel receives.

"This headlong rush for weapons increases the chance of war. It postpones peace negotiations. It defers economic development. It erodes security." Right on!