A Pentagon official said on Monday that major fighting in Iraq appeared to be over.
Major General Stanley McChrystal said US forces were moving into a phase of 'smaller, albeit sharper fights'.
The number of daily air missions had dropped to 700 or 800, down from about 1,000 or more, according to him.
Monday marked the last day that jets from all five aircraft carriers would fly missions over Iraq, he added.
The USS Kitty Hawk and USS Constellation could leave the Persian Gulf in the next several days, CNN quoted officials as saying. That would leave the USS Nimitz in the gulf.
One of the two aircraft carrier in the Red Sea, the USS Harry S Truman or the USS Theodore Roosevelt, could also depart, officials said.