OKINAWA—I've had to wait on the tarmac for planes ahead of mine to take off before, but never F-15s. Naha airport here shares a runway with Japan's Air Self Defense Forces, leading to delays whenever Japanese fighters scramble to counter Chinese incursions into the airspace above the Senkaku Island Chain in the East China Sea. The pace of such incursions has accelerated over the last half decade. The Japanese scrambled a high of 1,168 times in 2016, mostly in response to Chinese activity. The sight of active afterburners on a U.S. commercial runway would be shocking. In Okinawa, it's everyday life.