American Airlines’ parent company is seeking Chapter 11 bankruptcy protection as it seeks to unload massive debt built up by years of accelerating jet fuel prices and labor struggles.

The nation’s third largest airline also said this morning that its CEO Gerard Arpey will step down. He’s being replaced by Thomas Horton, the company’s president.

Fort Worth, Texas-based AMR Corp., along with its regional affiliate AMR Eagle Holding Corp., said today that they filed voluntary petitions to reorganize.

American says it sought protection to reduce its costs and debt to remain competitive. The airline will continue normal flight operations during the reorganization.

American is the only U.S. legacy airline that hasn’t filed for bankruptcy protection. The last major airline to file for bankruptcy protection was Delta in 2005.

American says labor-contract rules force it to spend at least $600 million more than other airlines. That’s partly a result of AMR avoiding bankruptcy last decade, while airlines like United and Delta were able to scrap existing labor contracts after filing Chapter 11.