Despite a new setback, Spirit AeroSystems will continue efforts to sell off assets used to build wings and other parts for the Gulfstream G280 and G650 business jet programmes.

The Tulsa, Oklahoma-based chapter of the United Auto Workers union, which represents the G280 and G650 workers at Spirit AeroSystems, rejected a proposed revision to the existing collective bargaining agreement in a vote on 28 September.

Spirit AeroSystems proposed the revision as parts of its efforts to complete the sale of assets use to produce the wings and other components of the two Gulfstream jets.

In a flier sent to union members, the UAW said the vote was necessary “as part of an asset purchase by the Triumph Group”. The message appears to identify the potential buyer of Spirit AeroSystems G280 and G650 assets, which has not otherwise been disclosed.

A representative of the Triumph Group did not immediately respond to an email seeking comment.

Spirit AeroSystems did not address the possibility of the Triumph Group as the buyer, but released a statement saying that the negative vote by the UAW in Tulsa would not derail their attempts to find a buyer.

“We are proceeding with the possible sale of the Tulsa operations,” a spokesman says.

Offloading the unit in Tulsa has been a central issue in Spirit AeroSystems’ strategy to recover from nearly $2 billion in announced writedowns within the past two years.

The Tulsa-based G280 and G650 programmes alone accounted for $1.2 billion of those forward losses, despite being a relatively minor part of the company’s overall business.