SEATTLE -- Sometime in the next five weeks, the stock price of UAL Corp. could move $40. The question is: Up or down?

The answer may hinge on whether ex-Chrysler Corp. executive Gerald Greenwald can persuade Boeing Co. Chairman Frank Shrontz to invest as much as $1 billion in a precariously leveraged airline directed by a fractious group of labor leaders.

Welcome to the wacky world of the United Airlines buyout. UAL Corp. is the parent of the giant Chicago-based carrier.

After months of offers, counter offers, failed bids, government interference and the threatened proxy war -- not to mention a phenomenal run-up of UAL's stock price last fall to nearly $300 a share, followed by a dizzying crash that reverberated through the stock market -- it's come down to this: Greenwald on a globe-trotting quest for cash, with a covetous eye on aircraft-manufacturer Boeing's bulging pockets.

On the table is a tentative buyout by unions representing United's pilots, flight attendants and machinists for $201 a share, or $4.38 billion in cash, debt and union concessions. The offer has been accepted by a controlling group of large shareholders and is contingent upon the employee-buyout group securing financing by Aug. 9.

Greenwald, the one-time heir apparent to Lee Iacocca at Chrysler, was recruited as the employee group's chief executive and assigned the task of closing the deal. His hiring was, in no small part, meant to offset concern that labor leaders had limited expertise in running a multibillion-dollar corporation.

Last week, former Northwest Airlines senior executive John Edwardson joined Greenwald as the employee group's chief financial officer. Yet the word on Wall Street is that the big East Coast and international banks -- rather than gaining a sense of confidence in the proposal -- are, in fact, growing increasingly skittish.

''You're talking about a 100 percent debt deal in a very risky industry. There's no depth of management experience behind Greenwald. The contract employees are not behind the deal. There's no real equity investor. The general lending environment stinks. So what's good about this deal? Nothing,'' said Edward Starkman, airline analyst at Paine Webber Inc.

Meanwhile, five major U.S. banks expressed a willingness to become the lead lenders for a $4.38 billion employee acquisition of United Airlines, the union-led buyout group said last week.

But none of the banks has yet signed loan agreements, and they are insisting that a portion of the financing come from non-banking sources such as aircraft suppliers, said a union group source.

The five New York-based banks are Citicorp, Chase Manhattan Corp., Bankers Trust New York Corp., Manufacturers Hanover Corp., and Chemical Banking Corp., United's pilots union said.

Although the employee group has promised to make as much as $500 million in annual wage concessions over the next five years, as well as raise another $240 million through the sale of UAL's 50 percent interest in its lucrative Covia computer-reservation system, the banks want the group to come up with approximately one-quarter of the $4.38 billion buyout price in cold, hard cash. Given the tight deadline, there's only one practical way to do that: Find a partner willing to toss $1 billion into the kitty.

That's where Seattle-based Boeing comes in. Reports began circulating last month that Greenwald had met with Shrontz, as well as top executives from the jet-making division of General Electric Co.

The bait? The gargantuan order for new aircraft United has been widely expected to book sometime this summer, a deal worth perhaps as much $15 billion. The order could total 150 planes and very possibly include the first orders for the 777, Boeing's proposed new jetliner and a product being counted on to keep the jet maker's production lines humming into the next century.

In return for financing part of the buyout (possibly through the exchange of cash for preferred stock), Boeing and-or GE presumably would be guaranteed the inside track on the United order.

''Boeing would probably rather not do this ... but if the question is, 'You either help out or United doesn't order the 777,' that puts things in a different light,'' said Bill Whitlow, an analyst at Dain Bosworth Inc. who covers Boeing.

Paine Webber's Starkman said Greenwald may be playing a classic bluff. He points out that United's fleet of 439 jetliners is comprised mostly of Boeing jets with Pratt & Whitney engines.

Other industry experts say GE has more to gain by helping Greenwald out, namely a larger presence in United's growing fleet.

''Boeing will get the huge order anyway,'' Starkman said. ''If you've got the products your customer needs, why would you feel the need to jump in on a shaky deal to convince him to buy your products?''

A week and a half ago, United made a move that seemed to confirm that Greenwald was using the order for negotiating leverage in his scramble to secure financing to complete the buyout. The airline, which reportedly was about to announce the order any day, postponed any action until after Aug. 9, the buyout group's deadline for securing financing.

''It's obvious that what Greenwald wants to do is use it {orders} as a club to help him find a source for financing,'' said George Kohl of the New York investment company Spears Leeds & Kellogg, which owns UAL stock.

Still, conventional wisdom is that Boeing is the most logical "white knight."

Since a mild downturn in the early 1980s, the Seattle aircraft manufacturer has enjoyed an unprecedented boom, racking up a commercial-jet production backlog of more than $90 billion. A conservative approach to finances has resulted in shareholder's equity swelling to a record $6.37 billion, while long-term debt, at a mere $286 million, is negligible for a large industrial company.

Boeing could easily lend the United buyout group $1 billion and still maintain a very comfortable ratio of debt to equity, said Whitlow.

''It's not like they'd be playing bet the company,'' he said. ''Boeing's balance sheet is exceptionally strong.''

So why didn't Boeing long ago gallop to the rescue? Why not take a $1 billion gamble on the buyout group and sew up the 777 order?

Probably for the same reason the banks don't want to finance the proposal by themselves: The deal is fraught with risk.