Eight years ago John Myhre was browsing through a book about the Bermuda Triangle when all of a sudden one of its mysteries disappeared.

He was reading about the last radio transmissions from Flight 19, a storied group of Navy fighter planes that vanished on a 1945 training flight from Fort Lauderdale, Fla., purportedly because of alien forces, electromagnetic confluence, or some other geographic bogeyman stalking the ocean area bounded by Florida, Bermuda and Puerto Rico.

"The lead plane radioed that he was lost and appeared to be over the Florida Keys," Myhre recalled the other day. "Then he said he was over a single island and there was no land visible in any direction." As a charter and corporate pilot who had flown the Florida coast and the Caribbean for years, Myhre said, "I knew immediately where that island was. And I realized I knew what had happened to those planes."

Ever since then, Myhre, who was shot down twice as a pilot in Vietnam and knows what it means to be missing ("the other crewmen thought I was dead"), has been tracking Flight 19, one of the keystone mysteries of the Bermuda Triangle legend. He has searched for information in Navy and Coast Guard records. He's shared his theories with the sole surviving member of the Navy board of inquiry that looked into the flight. He has re-plotted the pilots' course so many times "my calculator's on its fourth set of batteries and they last 1,000 hours." He's quit his job as an air traffic controller, co-written a book about Flight 19, hired boats and search teams and even gone down in a research submarine off the Florida coast.

Now, he says, he's found one of Flight 19's planes. It's upside down and broken some 390 feet down on the ocean about 35 miles off Cape Canaveral. What he found will be visible tonight at 8 on NBC-TV's "Unsolved Mysteries," and if it doesn't convince all those who prefer the idea of satanic forces offshore, that's all right with Myhre.

"I'm doing this for myself," he says. "I know I'm right. But I also know I have to prove it beyond a shadow of a doubt."

The Lost Flight A Navy officer's son who grew up in Chevy Chase and Kensington, Myhre can't remember just when he first heard the story of Flight 19, which has been the stuff of television melodrama and tabloid hype for at least 40 years. But by now he can recite it backward.

It begins on Dec. 5, 1945, when 14 men in five Navy planes take off from Fort Lauderdale Naval Air Station at 2 p.m. for a routine three-hour training mission off the Florida coast. Their planes are TBM Avengers, Grumman-designed torpedo bombers that rank among the largest single-engine warplanes ever built. With a 46-foot fuselage, a 54-foot wingspan and a crew of three, the Avenger has a 1,600-horsepower engine and a 300-mph top speed and had been a deadly workhorse of World War II in the Pacific. Now, with the war four months over, the planes and their experienced crewmen are merely exercising.

Their mission is to take them almost due east to Bimini for bombing practice on a nearby target called Hen and Chicken Shoals, then farther east to Great Stirrup Cay, 123 nautical miles from the base. From there they are to turn northeast for 73 nautical miles to Great Sale Cay, then jog southwest back to Fort Lauderdale. Weather is sunny and unseasonably warm.

Everything is going according to plan at 3 p.m. when the planes regroup after bombing practice, and a fishing boat reports seeing them safely heading east. But at 3:40 p.m. a plane near the base hears a distress call from Flight 19. The flight's leader, Lt. Charles C. Taylor, reports that both his compasses are out and he's lost. "I am over land, but it's broken," he says. "I am sure I'm in the Keys, but I don't know how far down and I don't know how to get to Fort Lauderdale."

Some time later, Flight 19 disappeared without a trace.

A naval board of inquiry was convened but found itself unable to explain how 14 experienced airmen in five reliable planes could vanish into thin air.

The Bermuda Triangle legend was apparently born from an Associated Press story by one E.V.W. Jones who on Sept. 16, 1950 -- a slow news day -- wrote about a region off the Florida coast where a number of planes and ships had disappeared. Other news services picked up Jones's story, then pulp magazines, then books, until "The Bermuda Triangle" became part of our culture.

The stories fed on each other, the hyperbole building, until, eventually, there were reports that there had been a last transmission from Taylor: "I know where I am now. ... Don't come after me! ... They look like they're from outer space!"

"I've never been superstitious, but like everybody else, I found it intriguing," said Myhre the other day, in town for the 30th reunion of his class at Bethesda-Chevy Chase High School. "But when I ran across a more accurate version of Taylor's last transmissions I realized what had happened."

The island Taylor reported seeing with no other land visible "had to be Walker's Cay," Myhre said. "I've flown over it dozens of times and it's the only one of the hundreds of islands around {Florida} that's by itself out of sight of other land. And it's northwest of the Abacos, which, in fact, look very much like the Keys when you fly over them. Clearly if he thought he was in the Keys, he thought he could reach mainland Florida by flying northeast. But if he was in the Abacos," northernmost islands of the Bahama chain, "a northeast course would just take him further over the ocean. And that's what I believed happened."

Myhre believes the planes flew in formation, thinking they were headed for land, until they ran out of gas and crashed.

Though he made his discovery in 1982, Myhre says, it was several years before he nailed down his theory. Contrary to the legend, he discovered from the transcript of the board of inquiry investigation that Flight 19 had reported each course change by radio to the Fort Lauderdale base, and the time of each had been logged. So by computing the plane speed and the altitude, and plotting hundreds of courses, he was eventually able to match a course with what the pilots had radioed that they saw.

At 3:19, when Flight 19 made its first left turn, the planes were already off course, he said, because they reported being over open ocean when they should have seen Great Stirrup Cay. "So they climbed to get a better view. That's what I would have done. And they probably went through some cloud cover and when they came out they were looking down on the Abacos, which look like the Keys."

Taylor, now disoriented, clearly had some sort of compass malfunction, Myhre says, but apparently thought it was so bad he'd gone south into the Gulf of Mexico.

"We are heading 030 {northeast} for 45 minutes, then we'll fly north," he said, apparently following the chain of islands north thinking he'd find Miami.

"Change course to 090 degrees for 10 minutes," Taylor said at 5:03 p.m. They were now heading due east toward Africa.

At that point weather conditions began to deteriorate and the other pilots in Flight 19 began to plead with Taylor to head west. At 5:15 Taylor finally ordered his planes west. Those at the air base were relieved, believing the planes had enough fuel to keep flying until 8 p.m.

Minutes later, however, the base heard Taylor order his planes east again. He was apparently still convinced he was over the Gulf of Mexico. Myhre, though, thinks that after some confusion the planes continued west. About 45 minutes later a Coast Guard plane, its transmitter broken, heard another pilot's final message to his colleagues: "All planes close up tight ... will have to ditch unless landfall. When the first plane drops to 10 gallons we all go down together."

Undersea, a Tantalizing Find Other fragmentary transmissions led Myhre to believe the first plane went down at 6:04 p.m. and several years ago he plotted its position. He wrote the Navy. He wrote other Bermuda Triangle buffs. Most thought his theories interesting but not compelling.

Then in 1986 the space shuttle Challenger exploded and every piece of underwater search equipment in America was assembled to comb the ocean floor off Cape Canaveral for wreckage.

Among the organizations was Harbor Branch Foundation of Fort Pierce, Fla., which was contracted by the government to investigate scores of possible wreckage pieces detected earlier by sonar.

Much of it, remembers Tim Askew, Harbor Branch director of marine operations, was oil drums, ship parts and assorted jetsam of the sea. But one target turned out to be a plane.

"We came up on it in the sub, saw the propeller, and knew it wasn't Challenger stuff so we didn't look at it further," Askew said. "We thought it was a DC-3."

But Myhre, reading a news report that a plane had been found, was certain he knew better. He began scrambling to raise funds for an expedition.

This summer, with $25,000 raised by his two partners in what he now was calling Project 19, he contracted with Harbor Branch to return to the site. There, 2 1/2 miles from the position he had first predicted, he found a Grumman Avenger, its aluminum body festooned with oculina coral, its wings shading a giant grouper fully 200 pounds.

He pulled off several pieces but was unsuccessful in finding a legible serial number that would cement it as one of the planes in Flight 19.

"The other planes are further north, in much deeper water, I'm certain," he said. "This was just the first to ditch. And the tragic thing about it is he was only about seven minutes from land. If they'd just kept going west... ."

The television tape of Myhre's discovery is mesmerizing, the broken aircraft ghostly on the ocean bottom, a vision from another age. As the research submarine Johnson Sea-Link circles the wreckage and peels off pieces and the giant grouper lumbers across the viewing field, Myhre babbles excitedly. "We definitely have an Avenger here, friends!" he says. "Is that a serial number? I've got numbers on the brain." It would take a dead man not to share his passion and his vision, not to want to lift this mystery forever from the Bermuda Triangle and bring Flight 19 home.

But something seems puzzling. You can't quite place it. And then it hits you: The plane's landing gear is extended. If a pilot is ditching in the sea, wouldn't he belly-land instead?

"That is a potential problem," Myhre said, "but there are several possible explanations. If you use the flaps to land on this plane, the gear goes down automatically unless you hit an override button. The pilot could have panicked. Or he might have thought he could have been over land. It would have been dark by then... ."

He acknowledges that Navy records show a wrecked Avenger was once pushed overboard from a carrier not far away. Could this be that one?

"The only way we can be sure is to bring it up," Myhre says. That will take a barge and at least $30,000 -- money Myhre at this point doesn't have. "That may be the only way we can get the serial number," he says. "I want to bring it up and put it in the Air and Space Museum."

So far, he hasn't had much help with that dream, which leaves Flight 19 still aloft, winging free in the imagination. Doesn't he sort of like that, even a little bit?

"You don't understand," he says with a face that's starting to look almost haunted. "I've given my life to this thing. At this point, this is all there is." aCAPTION: John Myhre, who has attempted to unravel the mystery of Fligt 19, and a TBM Avenger like one of the five planes that disappeared off Florida in 1945.