After years of being content to let most customers come to it, the Soviet Union is using Western hard-sell techniques at a major international air show to market one of its most sophisticated fighters.

Impressive aerial acrobatics by MiG-29 fighters at this week's Farnborough air show, where there is a large Soviet sales team, are the latest example of the Kremlin's opening to the West.

The Russians hope to get more export contracts for the jet - known in NATO as the Fulcrum - particularly in the Third World and with their allies.

Their presence at Farnborough International '88 represents the most ambitious public effort to sell fighter aircraft beyond the borders of the Warsaw Pact.

Competitors at Farnborough targeted two specific motivations for the Soviet push: cost of manufacturing and fear that today's technology will be quickly obsolete on tomorrow's battlefield.

Skyrocketing production costs have led to fewer Fulcrums rolling off Soviet assembly lines. Some of the best pilots in the Warsaw Pact may never fly the MiG-29 because their nations cannot afford the hard currency Moscow wants for the plane. Thus the world market becomes more important.

About 170 of the nearly 700 MiG-29s in service have been delivered to foreign nations. India, Iraq, Syria, Yugoslavia and North Korea all have operational squadrons. Finland, East Germany and Hungary also are said to be potential buyers.

It is believed the Soviets are aiming the plane at the Middle East market where oil revenues produce an abundance of hard currency.

Then there is the technological dilemma facing the Soviets. Advances by the Americans, British, French and other Western jet makers may surpass the ability of the MiG-29 to survive aerial combat in the 1990s, even in the Third World.

The MiG-29's acrobatics at the air show mark the first time the Soviets have shown such an advanced fighter before a large crowd in the West.

The Soviet Union's interest in Western air shows comes, ironically, at a time when such shows have come under fire in the West after an air show disaster last month in Ramstein, West Germany, where an Italian jet crashed into the crowd, killing more than 55 people.

A MiG-29 performed one of the most celebrated aerial displays of the Farnborough show. It climbed vertically, hung for a moment high above the airstrip, then fell tail first - a maneuver called a tail slide - before roaring away.

Specialists have given the sleek twin-engine fighter high marks for its showmanship.