Airborne early warning and control systems are critical tools for monitoring expansive airspace. Compared to ground-based and naval radars, early warning and control aircraft can much more rapidly deploy to a contested zone and can generally track and identify sea-skimming aircraft and missiles from a longer range. They will be particularly useful to monitor the disputed Senkaku/Diaoyu islands , which are located approximately 400 kilometers (almost 250 miles) from the Chinese mainland and from Japan's southernmost prefecture of Okinawa. Flying at high altitude, airborne early warning and control systems are well suited to closely monitor air and vessel activity over and around the islands. Not only can they provide a more accurate picture of the area, but they can also control friendly aircraft in the vicinity using specially equipped computers, radar systems and communication devices.