Want to trade in your old jumbo jet? Boeing will deal

Would you buy a used plane from this man? Jim Blue is vice-president for international, military, and used aircraft sales at the Boeing Commercial Aircraft Company, a division created in June 1983 to deal with the planes piling up on Boeing's back lot as airlines traded them in for new Boeing craft.

''During the first six months I met a lot of interesting people,'' he says, with a certain understatement. ''We sell direct to end users - that is, airlines - not brokers.'' But it took Mr. Blue, formerly part of Boeing's highly regarded customer-service operation, a while to be able to separate the two.

''I had one guy offer me a load of Munsingwear for a 727. The guy was dead serious. But what am I going to do with all that underwear?

''And then there was a guy in Louisiana who had inherited $86 million. He wanted to buy a couple of 747s and start an airline between two little towns down there. But they were only 80 miles apart.''

Such characters notwithstanding, Blue's operation has so far sold 36 planes, including Lockheed, McDonnell Douglas, and even Airbus Industrie aircraft, along with Boeing planes.

Despite the chortle value of the operation, it is serious business, too. Taking in used planes, like an auto dealership, is something Boeing does to sweeten a deal with a customer.

''It used to be a very rare thing, but now almost everyone talks trade-ins.''

Analysts suggest that Boeing is probably chortling all the way to the bank. As the new aircraft market improves, it takes up the used-craft market along with it. Prices on used narrow-body craft - such as the 727, which just recently went out of production - are considered good, and Blue says that ''wide-bodies are starting to be in short supply.''

He adds, ''I don't think we're going to see a glut of used planes on the market.'' With fuel prices holding steady, the need to replace older planes with more fuel-efficient ones is less urgent, he says.

Selling an airline, particularly a young one, a used plane is a way of providing ''interim lift,'' says Blue, until the line becomes profitable enough to buy Boeings - preferably new Boeings.

The used-plane operation, like Boeing's service program, is part of the company's larger strategy.

''We act this way not because we're Eagle Scouts,'' Blue says, ''but because we're in this for the long haul.''