United Airlines and Continental Airlines announced a definitive merger agreement that would create the world's largest airline.

The companies expect to complete the transaction in the fourth quarter after obtaining regulatory and shareholder approvals. United CEO Glenn Tilton would become non-executive chairman and Continental CEO Jeff Smisek would become CEO of the combined airline, which would be named United Airlines and headquartered in Chicago. "The marketing brand will be a combination of the brands of both companies," according to the joint announcement.