(Reuters) - A federal appeals court upheld a district judge's decision to drop manslaughter charges against two former BP Plc well site managers over their roles in the 2010 Gulf of Mexico oil drilling disaster that killed 11 people.

Robert Kaluza and Donald Vidrine were the two highest-ranking supervisors on board the Deepwater Horizon rig when disaster struck on April 20, 2010, sending millions of barrels of oil into the Gulf of Mexico.

A three-judge panel of the 5th U.S. Circuit Court of Appeals on Wednesday dismissed 11 counts of seaman's manslaughter charges facing Kaluza and Vidrine.

The panel affirmed a district court's 2013 ruling, saying the men's responsibilities on the rig did not constitute the "marine operations, maintenance, and navigation" of a ship and so the federal law did not apply to them.

The indictment accused the men of "negligent and grossly negligent" supervision of testing at the well in the run up to the explosion.

BP has sustained more than $42 billion in charges from the disaster aboard the rig. The company is awaiting a separate ruling from a New Orleans federal judge, expected some time this year, over its fines under the U.S. Clean Water Act.

The case is USA v. Robert Kaluza; Donald Vidrine, Case: 14-30122.