Boeing Co. technicians voted to form the first collective bargaining unit at the planemaker's factory in South Carolina, scoring a rare victory for organized labor in a state traditionally hostile to unions.

The "micro-unit" will represent more than 170 flight-line workers, a small subset of the 7,000 or so mechanics who build Boeing 787 Dreamliners in North Charleston. Even so, the result gives the International Association of Machinists and Aerospace Workers a foothold in a so-called right-to-work state. Boeing said it would challenge the election, which it contended was in violation of U.S. labor law.

"Boeing continues to believe that this type of micro-unit is prohibited by federal law," the company said in a statement Thursday. "While we are deeply disappointed with the result and are appealing, we will come together as we continue to deliver on our customer commitments."