Nevermind the fact that

UAL

(UALAQ)

hasn't emerged yet from bankruptcy, investors have pushed up the company's shares by more than 50% in the wake of its recent earnings report.

On Tuesday, shares of UAL, which trade only over the counter as a bulletin board stock, were at it again, spiking to $1.76 early in the session, trading at nearly triple their usual daily volume of 4.7 million shares. Investors grew slightly more rational later in the day, though, paring back earlier gains. As of the early afternoon, United shares were up 25 cents, or 18.6%, at $1.60, on 13 million shares traded.

Since Oct. 30, when UAL unit United announced a slight operating profit for the third quarter, investors have been diving into shares, ignoring the risks in buying equity in a bankrupt company. In the last three sessions, UAL shares have jumped from $1.09 to an intraday high of $1.78 -- a 63% gain.

But even United, which wouldn't comment on the way its stock has been trading, admits that shares are likely to be worth nothing when the company emerges from bankruptcy sometime in the first half of 2004. The company has the following warning on its Web site, telling investors, "While United's stock continues to be traded on the bulletin board exchanges, the company believes its equity securities have little or no value and are highly likely to be canceled under the plan of reorganization."

Some analysts blamed day traders for the sudden surge in United stock.

"It seems like someone is day trading in and out of shares, but I don't know any reason you want to own it," said Helane Becker, airline analyst at The Benchmark Company, a brokerage firm. "It's got to be day traders. No institution would go near it with the company bankrupt and that equity not worth anything."

Driving day traders may be an irrational hope that shares of United will show the same kind of upside strength rival network carriers have shown. After

AMR

(AMR)

, parent of American, dodged the bankruptcy bullet in spring of 2003, shares have gained more than 800%, with the company posting a surprise third-quarter profit.

But because of the way that bankruptcy works, there's little to no chance that United shares will even be able to perform like American shares. Under a plan of reorganization, United Airlines will reimburse creditors and bond holders with equity stakes in a brand-new company, leaving current equity shareholders out in the cold.

Investors hoping to profit from United's improving performance will have to wait until United reemerges from bankruptcy to do so.

Consider the case of

US Airways

(UAIR)

. Before the carrier declared bankruptcy in August of 2002, shares traded on the New York Stock Exchange under the symbol "U."

After the company filed for Chapter 11, the NYSE delisted US Air shares, which were then traded over the counter under the ticker "UAWGQ," while the company restructured. When the company went through with plans of reorganization and emerged from bankruptcy protection in April, those people who owned shares of "UAWGQ" got nothing, while creditors and bondholders received new shares in the company, which began trading under the ticker "USALA" on the over-the-counter market.

It wasn't until Oct. 21, nearly 15 months after US Airways filed for Chapter 11, that shares were once again listed on a major exchange. On that day, the carrier debuted under the symbol "UAIR."