* Appeals court dismisses case brought by ACLU

* Court votes 6-5 to end the case

SAN FRANCISCO, Sept 8 (Reuters) - A Boeing Co BA.N subsidiary prevailed on Wednesday in a lawsuit brought by plaintiffs who claimed its planes were used by the CIA to illegally transport them to secret prisons overseas, a federal appeals court has ruled.

The 9th Circuit U.S. Court of Appeals dismissed the lawsuit against Jeppesen Dataplan Inc, finding that rules protecting state secrets made it impossible for the litigation to proceed. The U.S. Department of Justice intervened in the case on behalf of Jeppesen.

A group of plaintiffs represented by the American Civil Liberties Union claimed they were tortured in the foreign prisons. An earlier three judge panel of the 9th Circuit had allowed the lawsuit, but the fuller court voted 6-5 on Wednesday to dismiss the case.

The case in the 9th Circuit is Mohamed v. Jeppesen Dataplan, 08-15693. (Reporting by Dan Levine; editing by Andre Grenon)