By Alwyn Scott

SEATTLE (Reuters) - Employees laid off by Spirit AeroSystems Holdings Inc in 2013 filed a lawsuit on Monday accusing the aircraft parts supplier of singling them out by age and disability.

Twenty-four plaintiffs were named and another 150 may join the case, attorney Daniel Kohrman, of the elderly nonprofit group AARP, said at a news conference in Wichita.

The lawsuit filed in U.S. District Court in Kansas seeks back pay, lost income and attorney's fees.

Wichita-based Spirit was spun off from Boeing Co in 2005 and is a major supplier to Boeing, Airbus Group SE, Bombardier Inc and other aircraft makers.

The plaintiffs said they were all aged over 40 when fired and that they or their family members had medical conditions that were or could be costly under a self-insurance health plan Spirit adopted in 2013.

"Spirit's senior management believed, based on knowledge of such conditions, that older employees ... posed a high risk of incurring large medical costs that Spirit would be solely responsible for paying, due to the company becoming 'self-insured' on July 1, 2013," the lawsuit said.

The former employees claim the company gave them poor performance reviews to justify laying them off, and did not rehire them when jobs for which they were qualified became open.

Spirit responded that it does not discriminate in hiring and firing workers.

"Reductions in force are never easy. However, all decisions are based on job-related, non-discriminatory criteria," Spirit spokesman Jarrod Bartlett said in a statement. "We are confident the evidence in this case will show Spirit is compliant with the law in its employment practices."

Spirit's shares closed 1.2 percent higher at $42.67 on the New York Stock Exchange.

(Reporting by Alwyn Scott; Editing by Richard Chang)