American Airlines parent AMR Corp. filed for bankruptcy after failing to secure cost-cutting labor agreements and sitting out a round of mergers that dropped it from the world’s largest airline to No. 3 in the U.S.

With the filing, American became the final large U.S. full- fare airline to seek court protection from creditors. The Fort Worth, Texas-based company, which traces its roots to 1920s air- mail operations in the Midwest, listed $24.7 billion in assets and $29.6 billion in debt in Chapter 11 papers filed today in U.S. Bankruptcy Court in Manhattan. Chairman Gerard Arpey will retire and be replaced by Thomas Horton, AMR said.