Three employees of Boeing Co.'s 787 campus in North Charleston have filed an unfair labor practice charge against a union recently at the center of a national dispute.

The National Right to Work Foundation said the complaint filed Wednesday with the National Labor Relations Board said the International Association of Machinists retaliated against workers at the nonunion plant.

The NLRB dropped a lawsuit against Boeing this month, moving to end the case after the Machinists approved a four-year contract extension with the aircraft maker.

The NLRB lawsuit said Boeing broke labor laws when it opened the North Charleston production line, punishing unionized workers in Washington state for past strikes. It also argued that Boeing should return the local 787 line to the Seattle area.

Boeing said it needed the South Carolina plant for valid economic reasons.