As a result of the Libyan Civil War, the United Nations enacted United Nations Security Council Resolution 1973, which imposed a no-fly zone over Libya, and the protection of civilians from the forces of Muammar Gaddafi. The United States, along with Britain, France and several other nations, committed a coalition force against Gaddafi's forces. On 19 March, the first U.S. action was taken when 114 Tomahawk missiles launched by US and UK warships destroyed shoreline air defenses of the Gaddafi regime. The U.S. continued to play a major role in Operation Unified Protector, the NATO-directed mission that eventually incorporated all of the military coalition's actions in the theater. Throughout the conflict however, the U.S. maintained it was playing a supporting role only and was following the UN mandate to protect civilians, while the real conflict was between Gaddafi's loyalists and Libyan rebels fighting to depose him. During the conflict, American drones were also deployed.

Answer this question, if possible (if impossible, reply "unanswerable"): What declaration ended a no-fly zone over Libya?
unanswerable