Are there such things as roads or expressways in the air?
Airplanes travel on arrival and departure routes, and airways that are clearly defined by geographic coordinates. Around 30 000 aircraft alone use Europe’s airways every day. For intercontinental flights, we have what we call “race tracks” crossing the North Atlantic, South Atlantic and Pacific, for instance. On routes from Europe to Hong Kong, we also use L888 (Lima triple eight), which passes over the Himalayas and considerably reduces flight time. But only modern aircraft with equipment and crews fulfilling certain requirements are permitted to use
How are airplane collisions prevented?
Air-traffic control coordinates the flight movements of all large passenger aircraft. The airport tower is responsible for granting the cockpit crew permission to take off and land and can thus ensure sufficient spacing between arriving and departing aircraft. After takeoff, the radar controllers at the large operating centers take over. They tell the pilots how high and what speed they should fly to maintain a safe distance.
Are there any technical warning systems that can alert the cockpit crew to the vicinity of another airplane?
Yes. There are technical warning systems on the radar screens in the cockpit. They show the cockpit crew the position of any aircraft whose flight path might interfere with their own. If necessary, the system will order an evasive maneuver; in other words, tell the pilots to fly higher or lower to avoid the other plane.