The Air Force and other military branches logged more than 500,000 flight hours in unmanned aerial vehicles last year, a spike that coincided with increasing troop numbers in Iraq. The drones were used most frequently in Iraq and Afghanistan, often flying missions 20 hours long, the Associated Press reported. Predator drone use more than doubled over the course of the year, from about 2,000 hours per month in January to about 4,300 hours by October. The 361 drones in Iraq flew more than 300,000 hours last year. To keep up with the increasing demand, the Air Force has transferred about 120 fighter pilots to posts in the United States flying the UAVs remotely. The increasing use comes as the military looks at ways to make UAVs more sophisticated by improving how they track targets and making their weapons more precise.