We had seen it all before. We have every unhappy reason to believe we will see it all again.

All three networks spent a large portion of the weekend trying to come up with something to tell viewers about the fate of the hijacked TWA jet that was being shuttled by its hijackers back and forth between Algiers and Beirut. Often when there was nothing new to report, the networks reported something anyway, either on the philosophy that viewers anxiously desired any sign of information, or on the philosophy that it was good business to do so.

By the time they got to their evening newscasts last night, the networks appeared to have settled in for a long haul, and from at least four corners of the globe they had gathered footage. You could feel the story tightening its grip on the nation. You could feel your neighbor watching in the next house. Last night's edition of "The CBS Evening News," with Dan Rather anchoring as he rarely does on weekends, was nothing less than state-of-the-art broadcast journalism that brilliantly summarized the crisis up to that point even as, Rather said, "this gruesome nightmare goes on."

Brit Hume on "ABC World News Sunday" called it "a three-day odyssey of terror." All the networks had more footage now and the story was branching out. CBS and ABC included reports on life in Richmond, Mo., the home town of John Testrake, the TWA pilot whose urgent messages from the cockpit -- "They are threatening to kill them NOW" -- had become as familiar as a slogan. Television was now in the process of making Testrake an overnight folk hero. There was enough real drama in this life-and-death story for a month of mini-series; a flight engineer's father, it was reported, had died of a heart attack, at least in part a victim of anxiety about the welfare of his son.

As the networks marshaled all their resources, foreign and domestic (CBS chartered Learjets to fly European correspondents to the Mideast), the hijacking of Flight 847 became almost literally the only national news story in America.

If the story of the terrorism is a story of the madness of the modern world, the television networks are a part of that madness even as they seek to document it. Yet for a change, this was a crisis not tailored for television. The hijackers did not seem to have "the media" in mind. Indeed, no network could get live pictures out of Beirut this weekend because the scars of that war-torn city include its satellite dish, out of commission for a year. Any videotape of the hijacked plane on the tarmac at Beirut airport was tape that had been shot by the networks, then driven dangerously by car to Damascus, the location of the nearest working satellite earth station, and then up-linked back to the United States.

This meant at least a three-hour delay in pictures. Sometimes, the tapes never even got through. CBS lost several cassettes when one of its cars was stopped and the tapes confiscated by members of one of several warring factions. All three networks say their drivers have been shot at. Sometimes networks send backup cars with extra copies of tapes in case the first batch does not get through.

"We try not to make them drive at night," an NBC News spokesman noted yesterday from New York.

Sometimes, in a strange way, and perhaps because we have become so accustomed to instant global video access to remote trouble spots, the very absence of live pictures can have the effect of making a breaking news story even more compelling, and more frightening, than if live pictures were available. If they can't even get TV cameras in there, we think to ourselves, this is a serious crisis indeed.

Pictures do not have to be live to be dramatic, of course. Nor even motion pictures. Some of the most dramatic broadcast portions of the crisis were the sounds of tape-recorded conversations between the pilot of the hijacked plane and the control tower at Beirut Airport. These recordings were played back repeatedly, always with high impact, often accompanied by nothing more visual than a freeze-frame picture of the plane as it sat on a runway.

Later there was dramatic film footage on all three networks of those passengers released by the hijackers, facing civilization, and the camera, again. What was not said by the passengers was as revealing as what they did say, because their words were obviously guarded in light of the ongoing crisis and the jeopardy still faced by those who remained in captivity.

What viewers saw most this weekend were the faces of network anchors, often talking by phone to correspondents in Beirut, whose still pictures were shown on the screen, sometimes superimposed on a map of the region. We saw a lot of maps. Also, there was the usual parade of witnesses called in on occasions like this, when little on-site footage is available. Experts on terrorism opined that the subject is only really confronted when such crises occur. That seemed the most inarguable sentiment of all those offered.

There were parallels between the government's handling of the hijacking and the networks' handling of the story. Both were extremely tense situations. As the government has not yet learned how to handle such acts of terrorism, neither have the networks decided precisely how most responsibly, and yet competitively, to cover them. As President Reagan flew back to the White House from Camp David in order to appear more involved with negotiations, so ABC News kept its anchor, Peter Jennings, prominently plopped before the camera so that he would look more involved with the coverage.

Harsh as it may be to say so, network news departments do see such frightening occasions as opportunities to promote themselves and their personalities. The decision to give Jennings a high profile in this coverage was probably not a purely journalistic one. Perhaps as a result, ABC seemed most eager to jump the gun in interrupting programs for "Special Reports" that were sometimes decidedly less than special.

Just before 2 p.m. yesterday, less than an hour after a previous "Special Report," ABC broke into programming again, and there was Jennings in his serious gray suit, having little if anything in the way of new developments to impart. Having earlier told viewers that "we're not too keen on reporting rumors," Jennings now offered the news, or rumor, that a hostage who had been let off the plane in Beirut "turns out, we think, to have been an old man who was ill." Jennings went on to report that "people are tense" in Beirut, that "it is now dark in Beirut," and that temperatures had reached 90 degrees that day in Beirut.

Finally, well into the report, a particle of news emerged from correspondent Charles Glass, to whom Jennings spoke by telephone. Glass said the hijackers had just announced they wanted the plane refueled and "they may be refueling the plane shortly." Surely the proper procedure for this "Special Report" would have been for Jennings to ascertain this information in advance and then lead with it once he got on the air. But somebody at ABC News decided the switch had to be thrown a few minutes too soon.

Viewers watching "This Week With David Brinkley" in Los Angeles saw a live Jennings update preempt the start of the show. When the Brinkley show was resumed, it was joined at a point at which Jennings, now on tape, was wrapping up a previous update some three hours old. ABC News spokesmen were proud of Jennings' performance on Saturday, however, when the continental anchorman, who spent 10 years in England reporting on Europe for ABC News, was speaking to a correspondent by phone from Algiers. The call was interrupted on the air by an international operator who, though speaking in French, seemed clearly inclined to disconnect both parties. Jennings, no dummy, spoke to the operator in French and in French asked her to leave the line open, s'il vous plait. She did.

Like Jennings, Dan Rather was very much in evidence on CBS News coverage. Although Bob Schieffer anchored the Saturday night CBS newscast, Rather was brought in (from the network's "Morning News" studio in New York) to report on the latest in the hostage situation, and those reports took up the bulk of the news time on the broadcast. He did the same on yesterday's late-night news with Charles Osgood. Rather and CBS were criticized recently when Rather failed to turn up for coverage of President Reagan's controversial visit to Bitburg, West Germany. The reason was primarily an internal political problem; the visit came during Charles Kuralt's "Sunday Morning" broadcast, and there was fear within CBS News that Kuralt would throw a temper tantrum if his province were invaded, even by the network's star anchor.

Rather, however, handled all the hijacking-related stories on yesterday's edition of "Sunday Morning."

A CBS News spokesman said yesterday that CBS had scored "the super-scoop of the weekend" when it was first to report, on Saturday night, that one of the relatives of a released hostage had said passengers with "Jewish-sounding" surnames were secretly taken off the plane and spirited into the city of Beirut. The State Department had a list of some of those names, the CBS spokesman said, and had notified some of the families. CBS and the other networks had the names as well, but did not broadcast them because of the delicacy of the situation.

If the networks were acting responsibly in most cases, they were also acting helplessly for the most part. The same stern visages of authorities on terrorism seemed eventually to materialize on all three networks as the long, anxious weekend wore on. What was there to do but talk, and hope?

Secretary of Defense Caspar W. Weinberger had already been scheduled as a guest on ABC's Brinkley show, but he was to discuss the Navy spy case. Obviously the topic was changed. But when Brinkley asked Weinberger if he could tell "anything we don't already know" about the crisis, Weinberger, of course, said no, he couldn't. In the same vein, it did seem terribly important for President Reagan to speak to reporters on the White House lawn when he got back from Camp David, but there was almost nothing definite or decisive he could say.

At NBC, meanwhile, it was decided less than 45 minutes before broadcast time to scrub the planned edition of "Meet the Press," an interview with Indian Prime Minister Rajiv Gandhi, and do the program on the terrorist incident instead. The decision to scrub was made at 11:56 a.m. "Meet the Press" went on the air at 12:30 p.m.

NBC anchor Tom Brokaw did not appear during any of this. He was on vacation in Africa, a spokesman said. Would he have been brought in to anchor coverage if he had been available? "Absolutely," the spokesman said. John Palmer of the "Today" show handled much of the special coverage.

We do tend to measure the importance of news on the basis of whether or not the networks dispatch their anchors to report it to us. During this frightening, angering weekend, the networks and their anchors were there almost as much to give comfort as to impart information. A venerable comforter, Walter Cronkite, will meanwhile be seen in prime time Wednesday night on a CBS News special, "Terrorism: War in the Shadows," scheduled well in advance of this weekend's ordeal. CBS spokesmen said it will be updated to include a report on the fate of Flight 847, whether its fate is known by then or not.

Because they had so little hard news on the story yesterday, networks were forced, with their experts, to consider the wider subject of terrorism and its effect on the world. What the crisis made horribly clear is that it's a topic that ought to be explored for reasons other than the fact that you can't get a live picture out of Beirut. How long until the next such calamity, with the same experts invited back to voice the same dire warnings? That's the real cliffhanger of cliffhangers.