The fate of a merger between two unions is up in the air.

The Sheet Metal Workers and United Transportation Union won’t be combining their organizations anytime soon.

Federal district court Judge John R. Adams issued a preliminary injunction June 25, putting the planned merger of the 80,000-member UTU and the 150,000 Sheet Metal Workers on hold indefinitely.

The ruling stems from a lawsuit filed by a group of disgruntled transportation union members who say they were not made aware of potential problems between the two unions’ constitutions before voting by mail last summer.

Adams’ decision means the merger, which was approved by both unions in 2007 after years of discussions, cannot take effect until the court fight is played out. It was to have taken effect Jan. 1. It would have created the International Association of Sheet Metal, Air, Rail and Transportation Workers.