May 20, 2011, marked the 60th day of US combat in Libya (as part of the UN resolution) but the deadline arrived without President Obama seeking specific authorization from the US Congress. President Obama notified Congress that no authorization was needed, since the US leadership had been transferred to NATO, and since US involvement was somewhat "limited". In fact, as of April 28, 2011, the US had conducted 75 percent of all aerial refueling sorties, supplied 70 percent of the operation's intelligence, surveillance, and reconnaissance, and contributed 24 percent of the total aircraft used in the operation. By September, the US had conducted 26 percent of all military sorties, contributing more resources to Operation Unified Protector than any other NATO country. The State Department requested (but never received) express congressional authorization.