He calls himself, mockingly, "the oldest jet pilot in America," but then self-deprecation is very much his style. Even if it were true, it would probably be the least of the distinctions assigned to Thomas J. Watson Jr.

His entry in Who's Who in America lists honorary degrees from 19 colleges and universities, including Columbia, Harvard, Yale, Brown and Oxford.

His honorifics include the Presidential Medal of Freedom, the Legion of Honor (France), the Order of Leopold II (Belgium), the Order of Merit (Italy) and the Royal Order of Vasa (Sweden).

He has served on the boards of Time Inc., the Mutual Life Insurance Co., Bankers Trust Co., Pan American World Airways and the New York Board of Trade, among others.

He is a former ambassador to the Soviet Union.

He is most famously the man who brought IBM -- or "The IBM Company," as he always calls it -- into the computer age.

But for today he is an old jet pilot, and he has just returned from Siberia.

The Great Adventure

On the nose of Watson's Learjet 55 is a runic legend that symbolizes the reasons a 73-year-old man would spend 16 days flying around the world: "ALSIB 1942-1987."

ALSIB stands for the Alaska-Siberia air route by which the United States sent planes to the Soviet Union under the lend-lease program during World War II. Watson, as part of that effort, flew the route in 1942; this month, he flew it again.

Watson, his grandson Willy and his copilot Robert Philpott took off from White Plains, N.Y., on July 5, bound for Moscow. The real point of the journey, however, was the next leg: a six-day trip over Siberia as the first foreigners to make a private flight over that territory since the end of World War II.

The object was to commemorate the opening, 45 years ago this fall, of the ALSIB route. Originally, most of the planes had been shipped by sea, either to northern Soviet ports or through the Persian Gulf; the Soviets were reluctant to exploit the more direct route across the Bering Strait, seeing an American presence in Siberia as a danger to Soviet neutrality toward Japan.

But, desperate for faster infusions of air power during the summer of 1942, Stalin agreed in principle to opening the new route. The details were worked out over several months of negotiations in Moscow, and the ALSIB route eventually aided the delivery of 8,000 aircraft from the assembly point in Great Falls, Mont., to the Soviet Union.

As an aide to Army Air Forces Gen. Follett Bradley, Capt. Thomas J. Watson Jr. was copilot of the crew assigned to fly the American negotiating team to Moscow in a four-engine B24 Liberator bomber.

"I suppose everybody has a great adventure," Watson says, "and my great adventure ought to have been 15 years running the IBM company."

But it was "somewhat dwarfed," Watson says, by the war years, which he still describes with a transfiguring enthusiasm.

Watson's commemorative trip obviously lacks the high-concept zing that some other titan-hobbyists have built into their escapades -- Malcolm Forbes, say, with his Bikes-to-Beijing. But then, Watson would argue that there is more involved here than a multimillionaire's adventure. One of the reasons he went was to promote peace by dramatizing a period of accord between the United States and the Soviet Union, he says.

"The ALSIB route represented the best cooperation post-revolutionary Russia ever had with the United States," he says. "The enemy then was pretty obvious ... very tangible. The enemy now is thermonuclear weapons -- much less tangible, much less easy to grasp. But they are a factor of millions of times more dangerous than the Nazis.

"I wanted to dramatize that unseen enemy we're all fighting," he says.

But let there be no mistake: Tom Watson also loves to fly for the hell of it.

The Captain of Industry

After celebrations Friday in Anchorage and Saturday in Great Falls, Watson stopped Sunday to rest a night in Dayton, Ohio, before making his way here. Meeting him there in the purple-on-purple lobby of a chain hotel, you would not take him for a Captain of Industry.

On the other hand, you would not take him for a native of Dayton, either. He is dressed more like Greenwich, Conn., where he has lived for 40 years: in the plaid of his jacket are the navy blue and acid green peculiar to enclaves East; in his loafers and cuffed khakis is the informality of serious money; on his tie is the insignia of the Mill Reef Club in Antigua, where he bought a winter home but rarely goes, because he still likes to ski so much.

The corporate culture inheres only in the button-down white shirt that was long the signature of IBM, and only in his brown socks is there a sign of the sort of disarray found in suitcases after a two-week trip.

Watson is tall and has good features -- regular features, free of any but the mildest idiosyncrasy. He has blue eyes, now hooded by age to the point that a smile renders them triangular. His perfectly rectangular white teeth look strong enough to slice hemp.

With his bifocals on he has the reassuring look of the pediatrician who should perhaps retire, but is beloved because he continues to make house calls. With his glasses off, called upon to play the role of elder statesman, he looks like a composite of every man who ever belonged (as he does) to the Metropolitan Club and the Council on Foreign Relations and the New York Yacht Club.

Watson joined IBM as a junior salesman in 1937, after graduation from Brown University. His father was the company's president. During his five years of service in the war, he says, he seriously considered making the Air Force his career. As he describes it, Gen. Bradley turned him around.

"Gee," said the general, when told of young Watson's plans. "I always thought you were going to go back and run the IBM company."

"General, we don't own that company," responded Watson, explaining that his father, hired out of Dayton's National Cash Register Co., owned very little stock.

The general shrugged. The car in which they were riding proceeded another few hundred yards. Said Watson, "General, do you think I could run the IBM company?"

The general allowed that indeed he did. Watson returned to IBM.

Watson offers this story in partial explanation of why World War II was such a crucial time in his life, and Gen. Bradley such a crucial influence. Once, when Bradley wrote the single word "splendid" on a report by his young aide, Watson was overwhelmed: "All the compliments I'd gotten in my life up to that time came either from my family or IBM people, who were being very nice to me because of my father."

It is clear that Watson overcame this modesty. He was made a vice president six months after returning to the company in 1946; a member of the board of directors four months later; an executive vice president in 1949, and finally president in 1952, when he was 38. Over the next 19 years he would also collect the titles of chairman and chief executive officer, before resigning in 1971.

But today Watson doesn't want to talk about IBM. He wants to talk about thermonuclear war.

'An Old Man's Dream'

The danger according to Tom Watson: "I just figure the more electronic gadgets you hook up, the more chance there is of an accident."

Hardly a sophisticated analysis, as nuclear theory goes; hardly an encouraging one, either, when you consider the source.

Watson has a canny approach to this business of proselytizing for peace. He is credentialed as a former ambassador and former chairman of the General Advisory Committee on Arms Control and Disarmament, in which role, he says, "I realized how many weapons we had, how many they had, and I decided to spend some time and some effort calling attention to how overarmed both sides were." He can talk with Anglican passion about the future of his grandchildren (12 of them, with a 13th on the way) and the "pitiful" state of U.S.-Soviet relations. He is a Democrat, and purveys on this business of arms control a decidedly liberal line.

He cannot quite be described, however, as a corpocratic Helen Caldicott. "I don't think any sovereign nation ought to trust any other sovereign nation," he says. "But I believe we can make treaties that can be verified."

Ask whether private endeavors like his advance the cause of world security and he says, "Oh, not particularly, no ... I think the amount one person can do is infinitesimal. Infinitesimal. But everybody who has the time and knowledge should be thinking about this."

"I don't think it's going to do very much good," he says at another point. By making no great claim for his efforts -- or even for his opinions -- he seems to confer on them an unassailable propriety.

When Jimmy Carter nominated Watson as his second ambassador to the Soviet Union, editorialists observed that he was no George Kennan. Nor even a W. Averell Harriman, whose service in Moscow during World War II was the most recent precedent for appointment of an ambassador there not drawn from the ranks of the career foreign service. As Watson himself says, "I didn't even know the basic things about being a diplomat." The 15 months of his tour did little to change expert opinion.

But even his detractors acknowledge that he had the bad luck to be appointed on the eve of the Soviet invasion of Afghanistan, which plunged U.S.-Soviet relations to their lowest point in a decade. "Our mission was frozen," Watson says now. "I was treated with cold respect."

Watson's most recent trip, which was undertaken in partnership with Brown's Center for Foreign Policy Development, included a week of meetings in Moscow. By week's end, Watson and Brown President Howard R. Swearer signed an agreement with the Soviet Academy of Sciences and the Institute for U.S.A. and Canada for a program of discussions and conferences, including a joint effort to define "mutual security."

Watson refers most questions about these Moscow meetings, however, to Mark Garrison, a former career foreign service officer who served under him in Moscow as deputy chief of mission, and who is now the director of the Center for Foreign Policy Development.

Watson prefers to talk about the trip: from Moscow to the university town of Novosibirsk, on to Yakutsk, where on the return to America in 1942 he and his comrades were stranded for two weeks after losing two of their B24's four engines in 30-degree-below-zero weather. Their landing in Yakutsk was so dicey that Watson and the pilot received decorations for it; the B24, temporarily crippled, was left behind as the only heavy bomber given the Soviets under lend-lease.

It took Watson 10 years to receive permission to retrace his steps, and he loved every minute of it -- even Anadyr, the last fueling post in Siberia, a town Watson calls "an absolutely dismal place. No one has been able to tell me why it exists."

At each stop, air veterans of the war were assembled by the 50 and the 100; several remembered bits and pieces of the mission 45 years ago.

Watson describes it as "the conclusion of an old man's dream."

At the Controls

"My skills are declining, obviously, because unhappily age does that to you," says the oldest jet pilot in America. "You don't fly at 73 -- if you've got any sense -- without somebody in the other seat who knows more than you do."

All this Old Man talk is a little hard to credit, for Watson seems a model of grace in his years. He is unembarrassed about asking for help with the recollection of a name, about groping for his glasses or discussing the hearing aids he wears in both ears; he emerges seeming not remotely hampered by age.

He takes the controls in Dayton, as he has done at every stop through 24 time zones, leaving it to his longtime copilot, Robert Philpott, to check lists and handle charts and explain to a visitor the delicate machinery of the four-year-old Lear.

Capable of reaching an altitude of 51,000 feet and a speed of about 600 miles per hour, this is the thoroughbred filly of private planes, a ride so smooth it might be a Rolls-Royce on a new stretch of tar. Watson deflects questions about the cost of keeping such a pet, saying that his wife is the only person he's ever told the price; but a brand new Learjet 55 runs somewhere around $5 million these days.

With a cellular phone, a stereo tape deck, an icebox, hot water, and plush seats that adjust three different ways, it seems a very good way to tour Siberia.

One shouldn't be fooled, however. Watson, who has 16,000 hours of flight under his belt, decided five years ago that after roughly 50 years of flying, a course in stunt flying might be fun. Bending his wrist back at a 90 degree angle, he describes something called a Hammerhead Stall, which he once performed over his summer home in North Haven, Me., for the pleasure of allowing his grandchildren to say to their friends, Oh, that's only my grandfather.

On the way to National Airport Watson dawdles. A fuss is scheduled upon his arrival at 11:00 a.m. -- photographers, champagne, Brown University officials and so on -- and Watson is nothing if not precise.

At the appropriate time, figuring five minutes to taxi to the Butler Aviation terminal, Watson aims the plane gently down runway 36, bringing the wheels down with a kiss of tarmac. Just shy of the terminal he turns to Philpott and, sounding tired for the first time, says: "One more landing and we're home."