Talk about good luck. A year ago, people at United Airlines were getting ready to slash their wrists because the $6.8 billion leveraged buyout of the company had fallen apart. Today, they ought to be sending thank-you notes to the Japanese bankers whose last-minute reluctance to lend blew the deal out of the sky.

Because, you see, if the $300-a-share deal had gone through, United would now be choking on a combination of high interest payments and Saddam Hussein-inspired fuel bills, the way debt-ridden airlines like Continental, Pan Am, USAir, Eastern, Northwest, TWA, Midway, Hawaiian Airlines and America West are doing.

Instead United, like the country's two other major, relatively debt-free airlines -- American and Delta -- can stand the strain of higher fuel bills because its balance sheet is relatively debt-free. In fact, United has just ordered new airplanes, and is in a dogfight with American for the right to buy choice European routes from debt-ridden Pan Am, which is again selling prime assets in an attempt to keep itself afloat.

The fact that United was lucky rather than smart is beside the point. If you compare the United that is to the United that would have been, you begin to see why loan officers have long been careful about lending to airlines.

The reason, when you think about it, is obvious. Airlines can be very lucrative, but they're also very risky. There are expensive planes to buy, unpredictable fuel costs to meet, fickle customers to lure. As Chairman Herbert Kelleher of Southwest Airlines said in an issue of Forbes magazine earlier this year, "You {can} go from spilling cash to bleeding red ink like the Mississippi River going through the Delta."

Risks like those are known as "operating leverage." Any time a company with operating leverage borrows a lot of money, it's piling financial leverage onto an already volatile balance sheet. This doesn't merely add risk to risk -- it multiplies the risks. It's the financial equivalent of mixing drinking and driving.

But because shrewd and lucky financial operators like Frank Lorenzo of Texas Air Corp. (now Continental Airlines Holdings Corp.) seemed to be the wave of the future, the old rule about not combining operating risk with financial risk went out the window.

Any airline that wasn't loaded with debt was accused of not having done the right thing by its shareholders. Analysts snickered at Delta for not being daring enough. Marvin Davis, the California billionaire, raided United. Donald Trump, then a real estate mogul, now a deadbeat, was threatening to raid American.

Who's laughing now? Northwest Airlines, which went private in a leveraged buyout that Chairman Al Checchi boasts is two years ahead of schedule in repaying its debt, is talking about "major layoffs." Hawaiian, another LBO, is on the brink of financial failure. TWA, hocked to the eyeballs by Carl Icahn to buy out its shareholders and make huge payments to him, is choking. Braniff has gone broke for the second time. USAir, which borrowed heavily to buy other carriers, is being squeezed, as are Midway and America West.

"We have proven that airlines are not candidates for LBOs," Pan Am Chairman Thomas Plaskett told a group of travel agents earlier this month. "They generate enough operating and financial leverage on their own, let alone adding to the leverage to provide payouts to shareholders." Indeed.

Then there's our old friend Continental Airlines Holdings. The news leaked last week that Continental had considered filing for Chapter 11 but decided not to do so. The disclosure that the company had thought of filing for bankruptcy reorganization may well end up forcing the company into Chapter 11 because suppliers will probably cut back on credit and travel agents may stop booking Continental flights. They remember getting burned in 1983 when Texas Air put Continental Airlines into bankruptcy and again in 1989 when it was Eastern's turn to go belly up.

Continental, which had $2.6 billion of debt and long-term leases on its books as of June 30, not counting Eastern's multibillion-dollar debt, said that it is thinking of selling its foreign routes to help buy its way out of trouble. The problem is that Continental has pledged its foreign routes to the U.S. Pension Benefit Guaranty Corp., the federal agency that insures pensions. The PBGC got Continental to pledge those assets to guarantee payment of the shortfall in Eastern's pension plan, potentially some $565 million. Continental's press relations people, as usual, wouldn't take my call. I didn't even bother trying to find Lorenzo, whom I've called for more than 10 years, but who has never called me back.

But the Chapter 11 prospect makes Lorenzo's departure from Continental in August look more than a little suspicious. Lorenzo, you recall, bailed out with $27 million, thanks to a deal he cut with Scandinavian Airline Systems to sell his Continental stock and options for about triple the market price. That's continuing the pattern in which Lorenzo cut special deals with the company that put millions of dollars in his pocket at the expense of other shareholders.

Poor Frank. He said in August that he was leaving Continental to let SAS run it unhindered. Yeah, right. At least when the Titanic sank, the captain had enough class to go down with the ship.

OOPS DEPARTMENT: Last week, in my Boston Celtics column, I wrote that master limited partnerships will lose their tax breaks after 1997. I should have said "most MLPs," because the post-1997 rule doesn't apply to real estate and natural resource MLPs.

Allan Sloan is a columnist for Newsday in New York.