NEW YORK (CNN/Money) - The search is on for a new top executive for United Airlines, just days after the current one reached a tentative agreement on its last outstanding labor contract with the union representing about 23,000 employees.

United parent UAL Corp. said Tuesday it is conducting a nationwide search for a replacement for Chairman and CEO Jack Creighton, who has served just six months on the job.

Creighton was brought in after the International Association of Machinists (IAM), which owns 20 percent of UAL (UAL: Research, Estimates) stock, demanded the resignation of James Goodwin last October. The union said it wanted stronger leadership and better communication with workers and was also angered by comments Goodwin made questioning the future of UAL in the face of post-Sept. 11 losses.

"I was brought in for the short term to stabilize United and improve the relationship between management and employees," Creighton said in a statement. "We have made some important strides in each of these areas, and I will continue to focus on those priorities as we search for my replacement."

On Friday United agreed to a costly new contract with the IAM for ramp workers, customer service and other employees that will make the union members the industry's best paid for their job classes but opens the way for concession talks.

The IAM took mechanics at United to the brink of a strike before reaching the industry-leading contract for those members. A statement by United management after the agreement said that it was a step that needed to be taken before the start of concession talks.