An Israeli delegation arrived here today to open face-to-face talks with Egyptian officials aimed at ending three decades of war and hostility.

As their blue-and-white El Al jetliner rolled to a halt at the ned to the runway at Cario Airport, the cockpit windows opened and three crew members who had been Egypitan POWs hung out little Israeli and Egyptian flags.

They were the only banners on display for the low-key arrival of the Israeli delegates who were quickly whisked off to the Mena House Hotel where formal Middle East peace talks willget under way Wednesday.

A preliminary discussion took place tonight when Eliahu Ben Elissar and Meir Rosenne of Israel met with Esmat Abdel Miguid and Osama el Baz of Egypt in a Mena House hotel room.

Sources said they talked mostly about the agenda for Wednesday's session, which will also be attended by representatives of the United States and the United Nations.

The American delegation, headed by Under Secretary of State Albert Atherton, also arrived here today. The United Nations will be represented by the head of the U.N. peacekeeping force in the Mideast, Gen. Ensio Silaasvuo of Finland.

Although both sides appear to feel they are on the verge of an historic breakthrough in the politics of the Middle East, seldom has an international conference of such potential importance opened with less preparation.

Both sides are operating in what senior Israeli officials have called "a thick fog." Neither side really knows what to expect from the upcoming talks, nor whether any of the positions they have prepared will be acceptable to the other side.

The Egyptians say they will first listen to Israel's response to the positions outlined by President Anwar Sadat on his historic mission to Jerusalem. The Israelis, on the other hand, say they will listen to Egypt's views on where there is room for compromise and where no compromise is possible.

It is the Israeli view that if any major progress is to be achieved, it will have to be done through secret diplomacy - far from the public eye.

Both sides generally concede that the present phase of the talks is likely to be confined to exploratory probes. If real substance is going to come out of Cairo, the negotiations will have to be held on a higher level.

Cynics say that the Israeli delegation, at this stage, can do little more than hold the telephone line open for Israeli Prime Minister Menahem Begin.

Still, many observers here have a strong sense that what may be an irreversible process is about to get underway. For all the lack of pageantry, there was no mistaking the arrival of the Israelis today for an ordinary event.

As the El Al 707 - with the word "peace" painted on its nose in Arabic and Hebrew - taxied to a stop next to regularly scheduled Austrian and Iraqi airliners, airport workers crowded around to wave and stare.

There were no cheering crowds on the Cairo airport observation deck, however. It had been cleared for security reasons.

Egyptian immigration officials came out to planeside in a special bus to process the Israelis' passports. They dispensed with the normal customs inspection.

As the flight crew and the Israeli hostesses watched from the top step of an Egyptian ramp, the Israeli journalists on the plane boarded a waiting bus and the members of the negotiating party - including Maj. Gen. Avraham Tamir in uniform - were escorted onto a helicopter and whisked away.

The Egyptian military helicopter took the delegates across Cairo, of which they saw nothing, to a landing pad at an officers' club near the Great Pyramids and the Mena House hotel.

Security precautions around the Mena House, which is 10 miles from central Cairo, were the tightest in memory. SOme 1,000 blue-uniformed riot police have cordoned off the area, and the hotel is sealed off to anyone who does not have the special pass issued for the conference.

Unfortunately for Egypt's tourist industry, the Mena House is at the foot of the main road to the Pyramids, which has been closed for the duration of the meeting.

The Israelis who arrived here today were certainly dressed for a historic occasion. Seldom have so many been seen in suits and ties.

The chief of the Isreali press office, Zeev Chafets, showed up at the Mena House in an elegant three-piece suit, which he confessed he bought just for this trip. He said it was "the first suit I bought in 16 years."

Leaden gray skies and gusty wind followed the Israelis into town today and rain slanted off the pyramids. That kind of weather is virtually unknown in Cairo, but it did not seem to depress the Egyptians, who are caught up in a fever of anticipation of peace.

At the Jolie Ville Hotel, where the non-Israeli press is quartered, the Feztopped doorman greeted guests with a big grin and a cheery "shalom."

Egyptian delegates who came out for a preliminary talk with their Israeli counterparts tonight seemed relaxd and at east, though they know difficult negotiations lie ahead. But the same cannot be said for the army of technicians called in to try to provide subordinate serives, especially communications facilities for the foreign correspondents.

The U.N. representative, Silaasvud, was temporarily blocked from entering the hotel by crates fo furniture stacked in the doorway.

There is also an acute shortage of Telex lines in Egypt, so the government, which wants maximum publicity for this event, simply requisitioned the Telex lines of some business establishments and ran them out to the conference site.

For all the upbeat mood at the Mena House, a certain amount of subsurface apprehension was evident on both sides. The Egyptians feel Sadat has gone out on a limb in his overture to Israel and that it is now very much Israel's responsibility to respond - and to respond favorably.

The Israelis, on the other hand, are apprehensive that despite Sadat's acceptance of Israel as a legitimate neighbor in the Middle East, they must be very careful about what they give up.

"The prime minister cannot prepare the beginning of the end of the state of Israel," a senior Israeli official said recently, "and leaders are only mortal. Sadat might not exploit our withdrawal, but suppose he is replaced one day another Nasser?"

In a surprise development, the Vatican announced that it would send an observer to the Cairo conference - perhaps in the expectation that the future of the Christian holy places in Jerusalem and in the occupied territories will be discussed.

In other developments, news agencies reported the following:

King Hussein of Jordan will visit Saudi Arabia on Saturday for talks with King Khalio, Riyadh Radio reported today.

The king will be continuing his efforts to end Arab differences resulting from the visit to Jerusalem last month by Sadat. Yesterday Hussein conferred with U.S. Secretary of State Cyrus Vance, who failed to persuade the monarch to join Middle East peace talks scheduled to start in Cairo tomorrow.

Secretary-General Kurt Waldheim has rejected an Egyptian proposal that his special envoy, Ensio Silassvuo, preside over the Cairo conference, a U.N. spokesman disclosed today.

The spokesman said Silaasvuo, would attend the conference only as an observer, to keep Waldheim informed of the proceedings.

Egyptian Ambassador Abel Halim-Badawi informed the secretary-general yesterday of his government's wish to have Silaasvuo preside over the conference, the spokesman said.

"This would not be in line with the functions of Gen. Silaasvuo," he said.

Waldheim's decesion to send Silaasvuo to the conference ran into opposition from Soviet and militant Arab circles that have criticized the Cairo meeting.

The U.N. General Assembly approved six anti-Israeli resolutions today, including one denouncing alleged torture of Arab civilians in Israeli-occupied territories.

The United States was the only nation voting with Israel against the resolution condemning alleged torture of prisoners, mass arrests, displacement of Arab civilians and destruction of Arab houses by Israeli authorities in Arab territories.

The vote was 98-2, with 32 absentions.

Israeli delegate Amiel Najar denounced the resolution as "deceiful and disgusting." U.S. officials opposed it because, they said, it was based on "questionable sources of information."

Another resolution adopted by the assembly condemns "massive, deliberate destruction" of the Syrian city of Quneitra during Israeli occupation in 1967-74. It reaffirms that Syria is entitled to compensation from Israel.