Shiite Moslem gunmen who yesterday hijacked a Jordanian airliner with 71 persons aboard blew up the plane at Beirut International Airport today after allowing passengers and crew members to leave.

The hijackers, believed to number five or six and armed with hand grenades, dynamite and other explosive charges strapped around their waists, escaped and disappeared into the Shiite-controlled suburbs near the airport, according to private radio reports.

Two Americans who were aboard the Jordanian airliner were hijacked again a few hours later when a Palestinian believed to be armed with a hand grenade and angry at the Shiite hijacking commandeered the Lebanese plane carrying them from Beirut to Cyprus.

But the passengers were able to leave the Middle East Airlines Boeing 707 when it landed at Larnaca, Cyprus, and the Palestinian, who had demanded the freeing of eight Jordanian security men aboard the first hijacked plane, was then flown to Amman, Jordan.

The two American passengers -- Landrey Slade, assistant president of the American University of Beirut, and his son William, 18 -- were trying to fly from Beirut to Atlanta to attend another son's graduation. "It wasn't bad," William Slade told The Associated Press from Larnaca, "but it isn't something we want to talk about."

The Shiite gunmen in Beirut said they had seized the Jordanian airliner and blown it up as a protest against a resolution by the Arab League that criticized the three-week-old refugee camp war being waged against Palestinian guerrillas by Moslem militias.

The Shiite hijackers released six crew members and the remaining 60 passengers on the Boeing 727 of Jordan's Alia airline this afternoon and dynamited the cockpit after several deadlines had expired. They had demanded that Arab League Secretary General Chadli Klibi come to Beirut to listen to their grievances.

In a communique issued at dawn today after a grueling journey from Beirut to Tunis, then to Palermo, Italy, and back to Beirut, then to Cyprus and back again to Beirut during the night, the "Brigade of the Marches of Lebanese Resistance" asked for the withdrawal of all Palestinian fighters from Lebanon and requested that they be distributed to other Arab countries.

Climaxing a 28-hour drama, the gunmen set off an explosion in the front of the plane. Witnesses then saw gunmen from outside the aircraft run under the plane and spray it with what appeared to be incendiary bullets. After the first explosion, a white cloud of smoke curled from the front of the plane. After the shots, the whole plane was on fire and within seconds was reduced to smoldering wreckage.

For a while the fate of eight Jordanian sky marshals who had been aboard the plane was unknown; there were some reports that they were still on the jet when it exploded. But Alia announced in Amman that the eight had been released with the help of the Amal militia and would be returned to Jordan.

Alia also announced that it was joining other airlines in suspending its flights to and from Beirut. The airline said the hijacked flight, bound from Beirut to Amman, had 65 persons and six crew members on board when it was seized. Five passengers, including a woman in a wheelchair, were freed during the night and this morning.

Private radio stations said the hijackers escaped and disappeared in the Shiite-controlled territory around the airport. Shiite Amal fighters are ringing the Palestinian refugee camp of Burj al Barajinah just east of the airport road.

The plane's Swedish captain, Ulf Sultan, later told reporters he had not believed the gunmen would do any harm after they backed down from a threat to blow up the aircraft over Tunis. Tunisian authorities refused the hijackers the right to land, forcing the Boeing 727 to fly to Italy Palermo for refueling.

He said the men appeared to believe in their cause and "all they wanted was to release their statement" -- a scathing attack against the Arab League for not aiding Lebanon and the Shiite community during the Israeli invasion of 1982.

Sultan described the hijackers as "young men who believe very much in their cause . . . . They were like a little army, each one fully equipped with dynamite, hand grenades and plastic explosives."

He described the atmosphere on board as relaxed and communication with the gunmen as easy. One hijacker told him, "I hope next time I hijack a plane that it will be the same crew," to which Sultan said he replied: "I hope next time I see you, you will have a ticket."