Drone powerhouse Israel is translating the knowhow of air force veterans to the delivery of sushi and ice-cream, as companies tap their expertise to avoid collisions in increasingly crowded skies. On a grassy stretch of a Tel Aviv beachfront, three drones fly above shiny high-rises this week, propellers buzzing as they lowered down onto landing pads. Two carry sushi, and a third hauls cans of beer. IMAGES AND SOUNDBITES