The USS Nimitz was a carrier in the United States Navy and, as of 2004, the lead ship of a battle group. The White House lost contact with it when Earth was attacked by Anubis. The ship was most likely destroyed with all the crew. (SG1: "Lost City, Part 2") The cover story for the loss of the ship and its battle group was that a 'meteor shower' had hit them, leading to the loss of 2,000 lives. (SG1: "Covenant")