Clutching each other for support, American hostages freed from the hijacked TWA airliner knelt down in the lobby of a tourist hotel here today to pray for their friends and relatives still on board the plane.

Unrestrained sobbing burst out as the Rev. P. William McDonnell, the leader of a group of pilgrims to the Holy Land from Illinois, referred to the terrifying experiences they shared as the hijacked plane shuttled back and forth between Beirut and Algiers. At least one passenger was shot dead by the hijackers as the plane landed yesterday in Beirut for a second time, and others were beaten.

As the released passengers got a chance to compare notes about their ordeal, a more frightening picture began to emerge of conditions on board the hijacked TWA airliner. When first freed, many hostages were reluctant to talk frankly to journalists for fear that negative radio reports might further enrage the hijackers, who are described as acutely "media conscious."

At the hotel, McDonnell said, "We pray that our captors are not unnecessarily cruel to those who are still in captivity. We pray for the crew and the flight attendants who were so strong and were able to help us."

"Oh Lord, hear our prayer," replied the former hostages in unison as buses waited outside to take them back to the airport for an Air France flight to Paris.

Edward Novak, an Algonquin, Ill., resident released yesterday with other elderly passengers, urged his fellow pilgrims to remember "the departed."

"Oh Lord, hear our prayer," came back the tearful response. This morning's impromptu prayer session, conducted after the hijacked jet again left Algiers for Beirut with more than 30 hostages aboard, turned into a cathartic outpouring of emotion after two days in which the passengers were forbidden to communicate with each other. The mood of the former hostages seemed a mixture of exhilaration at regaining their freedom and numb realization that the hijack drama continued.

Passengers described how they had heard an announcement made by the chief stewardess over the public address system at the demand of the hijackers as the plane came in to land in Beirut early on Saturday. The hostages, who had been forced to keep their heads between their knees, were told that they would hear "a noise" upon landing.

"Do not look up or this will be your fate, too," announced the chief stewardess, speaking under instructions at gunpoint from one of the hijackers.

As the plane touched down in Beirut, a scream and a shot were heard around the cabin. Later the stewardess, who since has been freed, was seen in the cabin with a bloodstained shirt, and a man's body was dumped on the tarmac of Beirut International Airport.

Ruth Henderson, an Australian tourist from Melbourne, said she believed that the victim was a member of a U.S. Navy diving team who had been sitting next to her during the hijacking. She said that at least two out of six members of the team were kicked and hit over the back of the head with clubs after being tied and blindfolded.

Several passengers said they thought that the other Americans with military affiliation or Jewish-sounding names may have been taken off in Beirut while the plane was there on Saturday night. But none could be sure as they were unable to see what was going on.

The behavior of the hijackers veered between the two extremes of brutality and kindness during the flight, according to the released passengers. The hijackers helped themselves to the personal belongings, money and jewelry of the hostages but also seemed solicitous about their welfare at times.

"They were like a bunch of kids taking the decorations off a Christmas tree," said Frank Scibetta of Geneva, Ill., describing how he was stripped of his watch, his travelers' checks, his pen and even his comb. "What they wanted, they kept. What they didn't want, they threw on the floor."

According to Scibetta, the floor of the TWA cabin was knee-deep in clothes and other personal belongings emptied out of overnight bags. The hijackers, who are believed to be Shiite Moslem extremists, put on T-shirts and cowboy hats belonging to passengers as they strode up and down the aisle.

One of the hijackers was even reported by passengers to have donned the captain's braided hat.

All the passengers were thoroughly frisked before being allowed off the plane -- and sometimes during the flight as well. Some were forced to leave all their personal possessions on board, including their wedding bands, while others walked off the plane clutching cases full of expensive video equipment.

By common consent, the most frightening moments were at the beginning, when the two original hijackers kicked their way into the cockpit brandishing grenades, and the landings at Beirut Airport. At one point it seemed as if the pilot might have to crash-land at the airport. The local authorities tried to blockade the runway and turned off the approach lights.

While the original hijackers who boarded the plane in Athens were clean-cut and presentable, accomplices who boarded in Beirut were dressed in combat boots, jackets, and T-shirts. There appeared to be some difference of opinion and rivalry between the two groups over tactics and strategy.

Still on board the plane are two American pastors from the Chicago area who took part in the pilgrimage: the Revs. James W. McLoughlin of Geneva, Ill., and Thomas J. Dempsey of St. Charles, Ill. Most of the hostages still being held are young American males.