Aeroflot, the Soviet airline now being banned by some Western nations in retaliation for the downing of the South Korean airliner, is one of the Soviet Union's most remarkable and mysterious creations.

Even by the measure of a nation obsessed with bigness, Aeroflot is big: the world's largest airline, far outstripping any other. It operates about 1,500 aircraft, from the specially appointed Ilyushin-62 that carries Soviet leader Yuri Andropov around the country to regular commercial jetliners, helicopters, biplane crop dusters and medivac choppers.

It is estimated that last year Aeroflot carried more than 100 million passengers to more than 3,000 Soviet cities, towns and outposts across the Motherland's 11 time zones. The airline, its planes with distinctive white and silver hulls, azure blue window stripes and a Soviet hammer and sickle flag on the tail, serves about 80 foreign countries. About a third of its 600,000 daily flight miles are logged abroad.

By contrast, United Airlines, which says it is the largest airline in the free world, has 329 planes and serves 129 cities, eight of them abroad. The 2,000 commercial airliners in the United States will haul about 300 million passengers this year, more than double Aeroflot's performance. Partly this is because of capitalism's well-known emphasis on ruthless efficiency. Partly it is because Aeroflot spends time on such chores as crop-dusting about 7 million hectares a year.

Since most of the airline's operations are in the soft-currency dominions of the U.S.S.R., the East bloc and the Third World, any ban on its flights to capitalist countries is unlikely to mean much financial damage. A Civil Aeronautics Board official has estimated that barring Aeroflot service for U.S. passengers probably would not cost the Soviets more than $2 million a year.

But Aeroflot statistics, so dear to Soviets, don't tell all the truth of this jumbo airline. In the strange world of Soviet reality, where fact and fiction enjoy an intimate daily relationship, Aeroflot occupies an important if surrreal niche in the country's psyche.

For an outsider aware of the U.S.S.R.'s closed borders and tightly restricted foreign travel privileges, few symbols seem so strange as the Aeroflot sign above Moscow's Kalinin Prospekt, a few blocks from the Kremlin. The rotating stainless steel ball, with pinpoints of light marking foreign cities the airline serves, brings proud glances from passers-by. If they realize that the foreign capitals are off limits to them, that the sign displays something they can never enjoy, they do not betray the thought.

And no one ridicules the model supersonic transport endlessly circling the globe in the opposite direction. That is supposed to be the TU-144, the premier Aeroflot airliner, better than the Concorde. It is among the airline's best advertised secrets. Service from Moscow to Alma-Ata by the crash-plagued Konkordski was announced with enormous fanfare more than five years ago. At the time I asked a senior Aeroflot official how many of the planes were available for the new service. "Enough," he replied. No announcement was made when the flights were abandoned a short time later after range problems couldn't be solved.

I flew Aeroflot all over the U.S.S.R. during four years in Moscow, and I'm here to write about it, so I have no complaints. But a domestic Aeroflot flight was almost always an interesting experience --from the woman at most ticket counters who used her nail scissors to trim the tickets, to the sweaty crush of embittered humanity at the bottom of the loading ramp who knew their seat assignments were fiction and that it would be every comrade for himself once the cabin door opened.

With relatively cheap fares and distances so great that only air travel makes sense, the monopoly airline's terminals are jammed with travelers year-round. Fuel shortages or bad weather, sometimes both, made borscht out of the flight schedules. It was almost impossible to get advance word about a possible flight. "Just go out there and wait" was the standard Aeroflot suggestion. As foreigners, we usually were treated far better than the Russians themselves--shunted to the front of waiting lines or through internal security points, provided a private waiting room, sometimes with buffet service.

But there was no way to soften the filing cabinet gray interior decor and thinly padded, narrow seats of the no-frills domestic service. Most internal flights played an important role in the flourishing private farmers' market system. There are stiff rules against stuffing ripe Georgian tomatoes into a cardboard suitcase, flying to Moscow and selling them in winter for six rubles apiece--about $9. But the Georgians and their resourceful Caucasus neighbors find ways to keep the trade going anyway. Flights out of Moscow smelled of sausage; flights into the capital smelled of fresh fruit and vegetables.

My wife, Eliza, and I were aboard an Aeroflot jet from the Central Asian Turkmeni capital of Ashkhabad to Moscow one autumn day when the surreal struck again. As the liner jolted down the runway toward takeoff, a strange, calming noise filled the cabin. I swiveled around in surprise: everywhere I looked there were huge, ripe yellow melons. On laps, under seats, in the aisles, in the racks above. They jiggled and sloshed in a delightful chorus. "If this cracks up, we're going to be okay," I yelled. "We're riding inside a Delmonte fruit cocktail can."

But that was from another era, before the Soviets taught the world new lessons about civilian travel.