Airspace: Class G
Altitude: 0–1200 feet
The FAA anticipates that within five years 7500 small commercial drones will be operating at these low altitudes. Current rules allow radio-control hobbyists to fly their aircraft within sight and under 400 feet. However, a new generation of small drones can go higher and follow GPS waypoints beyond a controller's visual range, raising worries about midair collisions with helicopters. Expected FAA restrictions may limit commercial drone flights to daytime hours, keep them away from helipads, and require an operator's license.
Airspace: Airports (Class B, C, D)
Altitude: 0–10,000 feet
Airspace surrounding towered airports consists of one or more tiered layers; the highest layer of the biggest (Class B) airports has a maximum radius of 30 nautical miles. FAA regulations require all aircraft operating in these airspaces to be equipped with two-way communication for exchanges with air traffic control (ATC). Even drones with a high level of autonomy will likely need to take off and land under ATC supervision.
Airspace: Class A
Altitude: 18,000–60,000 feet
This highly regulated slice of sky incorporates jet routes, where jet-powered drones could share the sky with airliners, military transports, and general aviation craft. As with manned aircraft, drones will have to carry transponders that provide location and altitude to air-traffic radar. In Class A airspace, pilots mainly rely on instrument readings rather than visual cues, except in the case of collision avoidance; because of this, unmanned aircraft will need yet-to be-developed sensors that enable them to detect and avoid other airplanes autonomously during an emergency.
Airspace: Class E
Altitude: All undefined airspace below 18,000 feet; everything above 60,000 feet
The upper fringes of airspace hold a lot of promise for pilotless craft. Here a drone could fly along an ATC-approved flight path without further communication, as long as it had a transponder and stuck to its course. High-flying drones are designed primarily for endurance, not speed, so the wake turbulence caused by faster manned airplanes could endanger them. Military jets also operate here, so high-flying drones would have to be able to sense and avoid supersonic aircraft—a big hurdle considering how quickly a drone would have to react.
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