"This flight has been hijacked," the pilot said in a steady voice."

That simple announcement over the PA system of TWA flight 830 began a bizarre eight-hour ordeal for 79 passengers and nine crew members that turned out to be a hoax that fascinated much of the world Friday.

Inside the plane the fascination was mixed with fear and nervousness. For the passengers on the half-filled Boeing 707, the first sign that something was amiss came when the plane stopped at 8:22 a.m. on an isolated landing strip about 1,000 feet from the terminal.

The pilot said: "We will be remaining here for an indefinite period of time: please remain seated and calm."

The 20 minutes later came the announcement of the hijacking.

The silence among the passengers could almost be heard. We looked at each other. There was no movement: no hijackers identified themselves. All we could do was look out the window for a signal.

As I learned later, a passenger in a black wig and moustache had thrust two letters totalling 21 pages into the lap of a stunned stewardess in the darkness of the early morning while the plane was over Ireland.

The hijacker told her to deliver the letter to the captain and not to return to the cabin. To avoid any possible panic the pilot did not divulge the letter's demands and instructions.

We did not know, sitting there as hostages that someone who said he represented an unknow group called the United Revolutionary Soldiers of the Council of Reciprocal Relief Aleverywhere had demanded the release of "a good German patriot," Rudolph Hess, Robert Kennedy's assassin, sirhan Sirhan, and "five brave Croation freedom fighters."

The letters displayed a knowledge of major hijackings of the past decades and contained instructions to the pilot as to where to land, how to communicate with the ground, what to tell his passengers and warned against violating his instructions.

The noise of the PA system crackled as the pilot's voice informed us that he was in touch with the "operations room" where the representatives of the Red Cross, the Swiss government and the U.N. ambassador had assembled. "They are doing everything possible to meet the letters' demands and to expedite the release of the plane."

At 11:15 a.m. the pilot emerged from the cockpit to walk through the plane. Ostensibly, he was there to answer the passengers' questions, but it seemed as if he was trying to see whether the hijacker would contact him.

He was barraged by questions but his answers offered us nothing new.

About noon the pilot informed us over the PA system that the authorities had not been able to contact the persons whose freedom had been demanded.

We satin limbo. There was no one to focus our fears on, no terrorist pacing the aisles, stocking pulled over a face, brandishing a gun. People were joking about the hijacker's method. The man behind me compared the situation to an episode on "The Twilight Zone."

I was seated behind a man sitting alone in his row who had drawn the suspicion of a number of other passengers, he spoke in a foreign accent and continually looked out the window at the activity on the airfield.

About noon, I was moved a few seats away from him. A TWA employe took my place, armed with a gin bottle which he seemedprepared to use if the man made anyabrupt moves for his blue airplane bag.

At 1:30 the pilot said that the Red Cross representative and the U.S. Ambassador to the U.N. were prepared to come aboard to negotiate.

"Will the individual or individuals concerned please indicate their willingness or unwillingness to proceed with these discussion," the pilot said.

He repeated this once and everyone seemed relieved when no one came forward.

The pilot came back over the PA system shortly after 3:30 p.m. to inform us that the two representative were now preparing to come on board. It was not until 45 minutes later, however that we could see two men in the distance begin approaching the plane. Exit ramps were pushed up to the plane.

A stewardess whispered to me that my father, the U.S. Ambassador to the United Nations in Geneva, was supposed to be coming aboard, but that I should show no sign of recognition to avoid becoming a special target for the hijacker. My eyes filled with tears for the first time.

A stewardess soon opened the door and a Swiss security official and TWA official, Stewart Long entered. Long told everyone that negotiators were ready to discuss all demands. He walked up and down the aisle twice looking for a signal from anyone willing to discuss the terms of the demands in the letter.But no one said a word.

At a signal, a stewardess opened the rear door and Long announced quietly that everyone should disembark in an orderly fashion. I got out first, and everybody else was on the ground within 90 seconds. It was 4:30 p.m.

I went to waiting bus, dizzy from feeling firm ground under me. Within minutes everyone was on the way to being interrogated by police in a heavily guarded area.

I ran from the bus to my father's arms. We held each other, weeping uncontrollably. It was a moment of exhileration and relief.

But there was still the nightmare of the police interrogation.

We all knew somebody in the room with us was the one who had delivered the letters that had threatened our lives. It must have been someone crazy who could sit so coolly and be questioned about his plans to blow up fellow passengers.

Now safely off the plane, I find the hijacking an experience, unlike any other.

When I called my sister in New York, she seemed jealous of the ordeal.

"I wish I had been on the plane," she said.