Two U.S. survivors from a hijacked Kuwaiti airliner arrived home yesterday without public comment and under tight State Department security, bringing to a close their ordeal of torture and terror on the wintry tarmac of Tehran's Mehrabad Airport.

The homecoming of New York businessman John Costa and Arlington auditor Charles Kapar of the Agency for International Development coincided with the disclosure of further details by the Kuwaiti ambassador here of the movements and identities of the four hijackers.

Ambassador Shaikh Saud Nasir Al Sabah said in an interview that the air pirates left Beirut last week carrying forged Lebanese passports, intent on a target that may have been deliberately selected because it carried Kuwaiti and U.S. officials.

"We tend to lean toward the fact that the hijacking was well-planned" with extensive intelligence and surveillance because the Airbus A300 jet carried three U.S. AID officials and three Kuwaiti diplomats, Al Sabah said.

"Was that coincidental or well-planned?" the ambassador asked. "It's not every plane that has three Kuwaiti diplomats and three American officials. It's not just a hijacking at random . . . . Suppose they hijacked a plane with no American officials? What would they have bargained with?"

Kuwaiti investigators, like their U.S. counterparts, are attempting to piece together the movements and identities of the hijackers. Two AID officials were murdered by the hijackers, and U.S. investigators are particularly interested in the extent to which Iranian authorities may have collaborated with the hijackers before overpowering them on Sunday.

Al Sabah said the four hijackers boarded a Middle East Airlines plane on Dec. 3 and flew from Beirut to Dubai on the Persian Gulf, arriving sometime before the Kuwaiti Airways jet with 161 persons aboard stopped briefly on its flight from Kuwait to Karachi, Pakistan.

The names used by the four were Druze or Sunni Moslem, Al Sabah said, although investigators believe that the hijackers were members of the Shiite Moslem sect who reportedly spoke with Lebanese accents. The ambassador said the names listed on the manifest, as reported by a Kuwaiti news agency, were Mohammed Al Daouq, Abu Shaqra and two listed only by the same last name, Alyafi.

"It's needless for me to say they were forged passports," Al Sabah said.

He said it remains unclear whether the four would have been screened again for weapons as they boarded the Kuwaiti Airbus in Dubai. The Airbus crew has said all passengers were screened before boarding, he added, which implies that the "catering corps" may have been in collusion by smuggling guns and rope aboard. That also would imply a broad, well-orchestrated conspiracy, Al Sabah added.

The real identities of the hijackers, who commandeered the Airbus and diverted it to Tehran shortly after leaving Dubai, remain a mystery. Al Sabah said -- and U.S. officials agreed -- that "there must be some affiliation" between the hijackers and the militant Al Dawa (The Call) sect, an Iraqi-born movement now believed based in Iran.

The only political demand by the hijackers during their six days in Tehran was the release of 17 prisoners now held in a Kuwaiti jail for the December 1983 bombing spree against U.S., French and Kuwaiti installations. Many of those prisoners, three of whom have been sentenced to death, are members of Al Dawa.

"For me to hijack an airplane on behalf of somebody, I must have some ties," the ambassador added. "It's our presumption, or assumption, they are from the same group."

A State Department official acknowledged yesterday that "we've got damned little to go on."

Another theory is that the hijackers are affiliated with the Hezbollah, or Party of God faction, another militant Shiite group linked to the bombings of the U.S. Embassy and Marine headquarters in Beirut last year.

"We sure as hell don't have anything that would pinpoint one or make one more likely than the other," one official said.

Another senior State Department official added, "We're not going to know for the longest time. Everybody's after hot news right now, but it's just going to take a while. It's like a police investigation and it's quite difficult when you're trying to investigate in a foreign country that's hostile."

The U.S. investigators are hoping for more clues when officials from the Office for Combatting Terrorism interview the two freed U.S. hostages. After arriving in New York at 1 p.m. from a U.S. air base in West Germany, Costa went directly home while Kapar flew here to his home.

Neither Kuwaiti nor U.S. officials have accused Iran of orchestrating the hijacking, although there has been considerable unhappiness with what was perceived to be an Iranian exploitation of the situation.

When State Department spokesman Alan Romberg was asked yesterday about Iranian assertions that U.S. aggression led to the two deaths in Tehran, he replied, "That's sick."

But Al Sabah said, "The way the Iranians handled the release, it took six days. But . . . let's assume that the Iranians stormed the airplane as soon as it landed. Much shooting and many victims fall. What would be world public opinion? You have to evaluate it from both sides."

Exiled former Iranian president Abol Hassan Bani-Sadr yesterday alleged that two of the Kuwait Airways hijackers had participated in the hijacking earlier this year of an Air France jet diverted to Tehran. Bani-Sadr, who fled to Paris in 1981, offered no firm evidence for his assertion.

"If what Bani-Sadr says is true, it makes the Iranian actions a good deal more disagreeable, if they're setting these guys loose to go forth and do likewise," a State Department official said. "Our general understanding was that hijackers who have gone to Tehran in the past had been detained. Not tried or convicted, but at least detained."

U.S. officials dismissed a proposal made Wednesday by Iranian Prime Minister Mir Hossein Mousavi, who said the Kuwaiti airliner's hijackers could be extradited only if the leader of an Iranian opposition movement is returned to Iran from exile in France.

"It's rather irrelevant from our perspective," one State Department official said. "I think it's more a question of trying to get them to live up to their responsibilities under the anti-hijacking convention," a treaty signed by Iran and many other nations intended to dissuade air piracy.

Another senior State official said that after watching how Iran handles the killers among the hijackers and evaluating the evidence of Iranian complicity, the United States will contemplate "everything from military options to sanctions to not doing anything."

Al Sabah said that either retaliatory action against terrorist groups or a preemptive strike in the future "is going to be a hard thing to do, if not impossible. Nobody knows where these groups are . . . . It's a given belief, even the president of the United States has said, that you cannot prevent terrorist acts."

Instead, he urged the United States to help solve the fundamental problems generating terrorism in the Middle East. "The core of this whole question is the Palestinian problem. Once we get that solved, the Lebanese question and others will fall into place. I would like to see the U.S. exerting more pressure on Israel," he added.