CHICAGO -- United Airlines chief executive James Goodwin resigned Sunday, saying it was time "for a new leader to guide the organization" which had greatly struggled since the Sept. 11 attacks.

Two weeks ago, a letter Goodwin (pictured, left) wrote was made public. In it, he predicted the troubled airline could perish unless its fortunes were reversed.

Two unions representing United employees called for Goodwin's resignation and the company's stock fell more than 20 percent last week in the fallout from the letter.

In a statement released Sunday, Goodwin said he was "proud to have contributed to the tremendous growth of United during my 34 years. ... United is a great company and it is the right time for a new leader to guide the organization through the challenges that lie ahead."

United parent UAL Corp. is expected to post operating of losses of $500 million to $600 million for the third quarter when it reports results this Thursday. UAL stock hit a 14-year low Friday.

United announced Sunday that John W. Creighton was elected to replace Goodwin by a unanimous vote of the company's board of directors. Creighton has been a member of UAL's board of directors since 1998. Earlier, he served as president and chief executive officer of Weyerhaeuser Company from 1991 through 1997.

"Our immediate goal is to restore United's financial stability," he said in a statement. "We intend to work hand-in-hand with our employees and unions to accomplish this task."

Sheri Meehleis of the Flight Attendants Union said that her reaction was "cautious optimism. We're looking forward to a new individual in place at the helm of United Airlines that will forge ahead and bring our company back to profitability and the number one position in the industry."

Meehleis said that Goodwin's letter to employees about United's potential demise caused a reaction from employees and investors.

"There were many obstacles that had presented themselves. Mr. Goodwin was giving us a lot more obstacles, I believe, that we didn't need to have to challenge at this time," she said. "Since Sept. 11, the airline industry has had a difficult time coming back into profit and into security with our customers."

"Mr. Goodwin sent a letter to all the employees at United Airlines several weeks ago and said that we were facing perilous times. While we all know that, and while we're all willing to forge ahead to create the atmosphere that will bring back our customers, there was a reaction from the employees, there was a reaction from Wall Street that perhaps set more obstacles in the path than needed to be," Meehleis said.

Airline Was Struggling Before Attacks

United already was in deep trouble before the terrorist attacks, suffering severely from the downturn in business travel, which it depends on more heavily than other airlines. Adding to its woes were the highest costs of any major U.S. carrier, including steep labor expenses.

The airline has laid off about 20,000 of its 100,000 employees since the attacks caused a drop-off in air travel. It also is trimming its daily schedule to 1,654 flights as of Oct. 31, down about 30 percent since the attacks.

United parent UAL Corp. is expected to post operating of losses of $500 million to $600 million for the third quarter when it reports results this Thursday. UAL stock hit a 14-year low Friday.

The Elk Grove Village, Ill.-based airline lost more than $700 million in the first half of the year, including as much as $116 million from the failed merger with US Airways which Goodwin proposed last year.

It was surpassed by American Airlines this year as the biggest U.S. airline.

United is the dominant carrier at both Denver International Airport and the Colorado Springs Airport, and some industry officials have expressed concerns that the airport will suffer if United's financial situation can't be improved.

Watch 7NEWS for local reaction and impact of Sunday's announcement by United.