The RQ-4 Global Hawk is a UAV that was developed and is currently being manufactured by Northrop Grumman. It is used by the United States Air Force as a surveillance aircraft. The United States Navy is also developing a maritime patrol variant, designated the MQ-4C Triton. The Global Hawk will eventually replace the Lockheed U-2, which is currently slated to remain in service until at least 2018. The Triton will complement the surveillance capabilities of P-8 Poseidon and also participate in intelligence-gathering and search-and-rescue missions. With a gross weight of over 30,000 lbs, the RQ-4B currently the largest unmanned aircraft in existence.