FARNBOROUGH, England - Bell Helicopter will team with an Israeli company in an attempt to develop a futuristic, vertical-takeoff-and-landing flying vehicle that would allow soldiers and police far greater mobility in urban environments.Bell unveiled a mockup of what the company has dubbed the X-Hawk on Monday at the Farnborough International Air show, one of the world aerospace industry’s major events for demonstrating technology and marketing aircraft and related products and services.The X-Hawk, as envisioned by Bell, would be an aircraft that could hold a pilot and up to 11 troops. It would be capable of navigating congested urban areas by...