Key developments in United Airlines history:
March 28, 1931 — United Air Lines Inc. incorporated.
March 20, 1939 — Signs industry's first collective bargaining agreement, with mechanics and related ground service employees.
July 1993 — Pilots, flight attendants and machinists unions agree to wage and benefit concessions in exchange for majority ownership of UAL Corp.
Dec. 15, 1993 — Unions reach a tentative agreement to buy the carrier in a $5.15 billion cash-and-concessions deal that would give them at least 53 percent ownership under an employee stock ownership plan.
May 24, 2000 — Announces it has agreed to buy US Airways for $4.3 billion in a deal that would give United larger operations along the East Coast and nearly triple its daily flights to more than 6,400 a day.
Aug. 26, 2000 — Agrees to grant industry-leading pay to its pilots after a summer of labor turmoil that resulted in thousands of flights being delayed or canceled.
July 27, 2001 — United Airlines and US Airways Group call off their merger after the Justice Department says it would sue to block it.
Sept. 11, 2001 — Two United planes are among the four hijacked by terrorists and crashed — one in Shanksville, Pa., the other hitting the World Trade Center.
Sept. 19, 2001 — Announces 20,000 layoffs in wake of terrorist attacks and decline in air travel.
Sept. 27, 2001 — Indefinitely suspends quarterly dividend, replaces chief financial officer.
October 2001 — Chief executive James Goodwin says the carrier "will perish" sometime in 2002 if it cannot soon stem huge losses that have worsened dramatically since Sept. 11. Stock plummets and union leaders call for Goodwin's resignation.
Oct. 28, 2001 — Goodwin replaced by board member Jack Creighton on interim basis.
Nov. 1, 2001 — Reports $1.16 billion quarterly loss, biggest in its 75-year history.
Feb. 1, 2002 — Announces $2.1 billion loss for 2001, a record for any airline.
Feb. 18, 2002 — Reaches tentative contract agreement with the union representing its 12,800 mechanics and aircraft cleaners, averting by less than 36 hours a strike that could have grounded the airline.
April 19, 2002 — Reports $510 million first-quarter loss.
June 24, 2002 — Asks the federal government for $1.8 billion loan guarantee.
Sept. 2, 2002 — Oil executive Glenn Tilton named chairman and CEO.
Oct. 18, 2002 — Stock sinks to $1.42 per share on the New York Stock Exchange, its lowest level in at least 40 years.
Oct. 18, 2002 — Reports $889 million third-quarter loss.
Nov. 4, 2002 — Stock soars 24 percent as company reaches a tentative $2.2 billion cost-cutting deal with pilots.
Nov. 27, 2002 — Mechanics reject a plan to contribute $1.5 billion in wage concessions that were part of UAL's effort to stay out of bankruptcy. In separate votes, two other factions of the machinists union approved the proposal.
Dec. 2, 2002 — Mechanics agree to vote on a revised contract that sweetens terms on benefits but still calls for wage cuts of 6 percent to 7 percent.
Dec. 4, 2002 — Federal Air Transportation Stabilization Board rejects United's request for $1.8 billion in federal loan guarantees.
Dec. 9, 2002 — United Airlines files for Chapter 11 federal bankruptcy protection in Chicago. It is by far the largest bankruptcy filing by an airline and one of the biggest by any U.S. company.