President Reagan, staging a bipartisan show of support for his embattled $8.5 billion aircraft deal with Saudi Arabia, won support from 16 prominent officials of past Republican and Democratic administrations yesterday in hopes of salvaging the sale from the threat of congressional veto.

While Reagan hosted a luncheon gathering of 13 of the former national security officials, Secretary of State Alexander M. Haig Jr. escalated another aspect of the administration's lobbying campaign by warning the Senate that it is a "dangerous illusion" to believe Saudi Arabia will agree to joint U.S. control over the Airborne Warning and Control System (AWACS) planes, the most controversial element of the proposed arms package.

The sale will be blocked if both houses of Congress vote against it before the end of the month. In the Senate, where the administration hopes to turn back the opposition, a potentially decisive group has declared it will vote for the sale only if the Saudis agree to some form of joint control over the AWACS radar surveillance planes.

These senators have associated themselves with a joint command proposal put forward by Sen. John Glenn (D-Ohio) on grounds that it offers the only way of ensuring that the planes are not used against Israel and are protected from falling into the hands of U.S. foes.

However, Haig, testifying before the Senate Foreign Relations Committee yesterday, said the Saudis would not accept any restrictions beyond an already announced "understanding" for joint security measures and use of U.S. military personnel to train Saudi crews for a period extending into the 1990s.

"I share Sen. Glenn's desire to see the best air defense capability possible," Haig asserted. But he added:

"The kind of joint command that he is talking about is simply not possible now. Therefore, there is absolutely no point whatsover in comparing the present proposal with some imaginary, even if highly desirable, joint command arrangement."

Haig gave the committee a list of the terms and conditions to which the Saudis have agreed. Most had been made public earlier, but the list revealed the fact that the computer programming "software," which U.S. officials say is the most secret component of the AWACS equipment, will remain U.S. property after the planes are turned over to the Saudis.

In his testimony, Haig also raised another point that is becoming an increasingly prominent theme in the the hard-sell being used by the administration on members of Congress.

That is the contention that if Congress rejects the deal, it will have to bear responsibility for severely damaging U.S.-Saudi relations and compromising efforts to induce Saudi Arabia to play a more active role in the Mideast peace process.

"The question is not whether Saudi Arabia will join the ranks of our enemies," Haig argued. "The question is whether Saudi Arabia will withdraw from a moderating role in Arab and Islamic councils and seek instead the protection that a lower profile affords . . . . It will not be easier for Saudi Arabia to run these risks if they are publicly rebuffed by their closest friend in the West."

A parallel note was sounded in a joint statement by the 16 former officials. It said, "The rejection of this sale would damage the ability of the United States to conduct a credible and effective foreign policy, not only in the Persian Gulf region, but across a broad range of issues."

Collectively, the officials have held offices including secretary of state, secretary of defense, national security affairs adviser and chairman of the joint chiefs of staff in administrations back to that of President Eisenhower.

They are Harold Brown, Zbigniew Brzezinski, McGeorge Bundy, Gordon Gray, Henry A. Kissinger, Melvin Laird, Lyman Lemnitzer, Robert McNamara, Thomas Moorer, William P. Rogers, Elliot L. Richardson, Walt Rostow, Donald Rumsfeld, James R. Schlesinger, Brent Scowcroft and Maxwell Taylor.

Reagan described the group as a "who's who" and, by any standard, it was a most remarkable assembly of national security experts that gathered around him on the North Portico of the White House.

Some had been on opposite sides of past feuds, and some are remembered for involvement with controversies such as the Vietnam war policy symbolized by many of them from Maxwell Taylor, moving with the aid of a walker, through McGeorge Bundy and McNamara to Kissinger and Scowcroft. Yesterday, though, past differences were submerged for unity on one weapons sale program.

In addition to Reagan, who thanked them for their support, Kissinger and Brown spoke briefly.

In the famous voice heard so often at the White House during the Nixon and Ford administrations, Kissinger said the sale is compatible with the security of Israel and necessary for "a credible and effective foreign policy." Brown warned that rejection would not help the security of Israel or the United States.

Earlier yesterday, Senate Majority Leader Howard H. Baker Jr. (R-Tenn.), conceding that "we don't have the votes now," said Reagan will meet with all Republican senators at the White House today and added: "I think the president can and will make a personal appeal."

White House deputy press secretary Larry Speakes said former president Carter, who supports the sale, is likely to visit Reagan when Carter is here next week and offer his support.

In the first test of strength over the sale, the Senate Foreign Relations Committee had been scheduled to vote Wednesday on a resolution of disapproval sponsored by 50 senators. However, some committee sources said a decision may be made today to postpone the vote until next week.

Haig, questioned hard about Reagan's statement last week that the United States will not permit Saudi Arabia to become another Iran, insisted that it did not differ appreciably from former president Carter's assertion that a cutoff of Saudi oil would be unacceptable to the United States and its allies.

Although he consistently turned aside questions about what circumstances might cause the United States to intervene in Saudi Arabia, Haig said a serious interruption of the oil flow would cause Washington to consult the allies "and take appropriate steps to deal with it."