The mufti Abdul Amir Qabalan, a Shiite Moslem leader with a white turban, black beard and gray robes over an imposing stomach, sat at the control tower microphone and spoke to the gunmen holding an airliner on the tarmac below.

"By everything that is holy to us, listen to my words," he exhorted them. "This is not a Libyan plane. It is a Kuwaiti plane. Oh, brother Hamzeh, this will not help the cause of the Imam Moussa Sadr."

Crackling from the blue and white Kuwaiti airliner came the response from Hamzeh, who with a dozen young comrades packing AK47 assault rifles had hijacked the plane hours earlier, "It is not possible for us to come out of this plane, even two months from now, until the Imam Moussa Sadr returns safe and sound."

By early this morning, however, Hamzeh and his fellow terrorists had come out of the plane. The 105 passengers and crew had been released unharmed. Syrian tanks ringing the airport had returned to their positions. Armed youths of various nationalities and persuasions had gone home for some sleep. And Lebanon's integrity had been bruised again in the name of another improbable cause from among the many here whose main expression is brutality.

This time it was a nine-hour hijacking by gunmen demanding the return of the Imam Moussa Sadr, Lebanon's Shiite Moslem leader who disappeared on a trip to Libya in 1978 and is widely believed to have been murdered by Libyan secret police.

The day before it was a pair of car bombs on a crowded seaside market street that killed half a dozen civilians and set fire to shanty-style shops thrown up by traders whose traditional marketplace was blasted apart long ago in Lebanon's civil war.

Overlapping both was a conflict in the northern city of Tripoli pitting ragtag street armies of local Moslems against the Syrian-financed and armed Arab Democratic Party militia--the Arab Cavaliers--backed by paratroops from the 22,000-member Syrian force here whose official mission is to police a cease-fire that was supposed to have ended the war more than five years ago.

One obstacle to efficient resolution of the Beirut drama, in fact, was the presence in Tripoli of Col. Mohammed Ghanem, the top Syrian security official in Lebanon, who was trying along with Palestinian leader Yasser Arafat to restore peace to that city after four days of street clashes that killed a dozen persons and wounded more than 50.

Arafat and one of his highest ranking military advisers, Saad Sayel, have been tied up most of the week mediating the Tripoli crisis. This has detracted them from what Arafat has been proclaiming for weeks is the main danger facing his Palestine Liberation Organization--his belief that Israel is poised to mount a large-scale attack in southern Lebanon to expand the amount of territory it effectively controls there and punish the PLO for assaults on Israeli territory.

An American returning after an absence of 19 months to this world of violence and threats of violence finds the array of conflicts here so varied as to seem madcap and the lineup of causes so intractable as to seem hopeless.

The temptation is to laugh, for example, on learning that the main government official dealing with the hijack on the scene was Marwan Hamadeh, the tourism minister, or on hearing that the Commodore Hotel, where most journalists stay, tried to send beer and sandwiches to television crews waiting out the crisis--only to be foiled by a Syrian tank on the airport road.

But the deaths and the grief the conflicts cause are real. Although estimates vary, the most conservative say more than 50,000 persons have died from acts of war and terrorism here since the country flew apart in 1975.

Blood still stains the sidewalk where the car bombs went off Tuesday. Apartment buildings are still a shambles where Israeli planes bombed PLO offices in a crowded residential neighborhood in July. A bearded youth in Tripoli is still bragging about how he lay wounded on the floor of his filthy makeshift clinic and administered to people with Red Cross medicines.

Moreover, the causes and the conflicts also are real, even if they have been stained by quick resort to violence. This was brought home with rare clarity as the mufti, Sheik Qabalan, and others conversed through the night with Hamzeh and his band inside the blue Kuwait Airways Boeing 707.

"We cannot go back," Hamzeh shouted over the airwaves as the mufti urged him to release the passengers.

Within minutes, one of Hamzeh's squad loosed bursts of submachine-gun fire toward the tower. Several red tracer rounds sailed gracefully through the night. Others pinged off the tower walls or crunched through the plate glass observation bubble.

"We will pull back the soldiers" surrounding the plane, the mufti continued, unperturbed as others in the tower cowered on the dusty floor. "But you must promise me by the absence of the Imam Moussa Sadr that we can solve this problem here in Beirut."

The imam's disappearance thus had become so sacred that one of his pupils was calling on the gunmen to swear by it. To mark the cause, the imam's successor, Mohammed Mahdi Shamseddin, has refused for three years to assume the title of imam, spiritual leader of Lebanon's 950,000 Shiite Moslems, although in fact he exercises the office.

"Sheik Mohammed Mahdi has delegated me to tell you that this thing must end peacefully," Qabalan insisted after conferring with Shamseddin over a walkie-talkie. The walkie-talkie had been provided by one of his Shiite bodyguards who were armed with submachine guns, machine pistols and hand grenades dangling from their combat vests.

Hamzeh complained, however, that Lebanon had not done enough to press the search for Sadr or pressure Libya's leader, Col. Muammar Qaddafi, to account for his disappearance. He insisted that the Lebanese government break relations and call a U.N. Security Council debate on the imam's fate.

"There is no Lebanese state," retorted Qabalan. "If there were a Lebanese state, this thing would have been solved a long time ago."

"The situation cannot be tolerated, oh brother Hamzeh," he went on. "I am your sheik. I am your mufti. You must talk to me. It is not possible that you refuse to listen to me."

After more than 90 minutes of patient appeals, Qabalan agreed with Hamzeh that airport utility vehicles surrounding the plane and preventing its takeoff would be pulled back 20 yards as a goodwill gesture. But minister Hamadeh, quietly and respectfully, insisted to the religious leader:

"If the cars pull back, the plane will take off. It is the opinion of the state, and the opinion of our brothers in Damascus who run the peace-keeping forces, that this thing should end here."

The hijackers had stormed the plane seconds after it landed in Beirut on a flight from Tunis to Kuwait with a stop in the Lebanese capital. Earlier, they had asked for fuel to fly to Tehran. The fuel had been refused, however, and Tehran authorities telexed back that their airspace was closed.

Without telling them that their insistence on having the cars removed also had been refused, Qabalan notified the hijackers that he was coming down to the plane. But as he drove up, firing broke out. More bullets smashed through the control tower glass. Several rocket-propelled grenades crashed down on the airport, fired from nearby Shiite-inhabited suburbs.

"The Lebanese Army opened fire on us," Hamzeh shouted over the radio. "I want to talk to officials of the National Leftist Movement, the government, whoever is responsible. We are going to take off whatever it costs."

The firing was a mistake, Qabalan insisted, speaking from a radio-equipped car where he had taken refuge. "Yes, it is a mistake I am going to pay for," responded Hamzeh.

But Qabalan persisted. Almost nine hours had gone by since Hamzeh and his comrades raced out to take over the plane, firing from a white Mercedes. He began to relent. By 1 a.m. today, he allowed a Syrian security office to come aboard, followed by a leader of the Shiite militia Amal.

Half an hour later, most of the passengers descended to safety. Six Libyan and two Lebanese passengers were kept as hostages as Hamzeh and his team drove off with the officer to a Syrian Army position. By 6 a.m. the eight hostages were released. Authorities refused to divulge the fate of Hamzeh and his comrades.

Jay Deeb Haidar, head of Lebanon's civil aviation security team, said the night's drama was Hamzeh's seventh hijack or attempted hijack in the name of the missing imam. Other Lebanese officials predicted there will be another soon.