The battlefield setbacks will likely increase calls for the international community to supply weapons to the lightly armed rebels.
The operation will be commanded by Canadian Lt. Gen. Charles Bouchard from NATO's operational center in Naples, Italy. There was no word on how many airplanes and military staff would be involved, but officials say dozens of fighters, fighter-bombers, air refueling tankers, AWACS surveillance planes, maritime patrol aircraft and search-and-rescue helicopters will likely be required for the operation.
They will be based at a string of NATO bases along the Mediterranean, including Italy, France, Greece and Turkey.
"The transfer of authority on air assets is now complete," NATO spokeswoman Oana Lungescu said. "Everything that has been offered to us has been handed over.
"NATO is the only one issuing operational orders for the international effort," she added.
NATO's governing body, the North Atlantic Council, has approved the alliance's operations for up to three months. That period could be extended if necessary, officials said.
Associated Press writer Karl Ritter in Stockholm contributed to this story.