US airspace classes and when you need ATC authorization

Airspace questions on the Part 107 test come down to one practical question: do I need permission from air traffic control before I fly here? Section 107.41 gives the answer. You need prior ATC authorization in Class B, Class C, Class D, and in the surface area of Class E designated for an airport. You do not need it in Class G, or in Class E that starts above the surface.

The classes in a few lines

• Class B surrounds the busiest airports, usually from the surface to 10,000 feet MSL, in layers shaped like an upside-down wedding cake. On a sectional it is drawn with solid blue lines.
• Class C surrounds busy airports with a tower and radar approach control. It typically runs from the surface to 4,000 feet above the airport elevation, with an inner circle of 5 NM and an outer shelf out to 10 NM. Solid magenta lines.
• Class D surrounds smaller airports with an operating control tower, usually up to 2,500 feet above the airport. Dashed blue lines, with the ceiling in a box such as [25] = 2,500 feet MSL.
• Class E is the rest of the controlled airspace. Its floor is often 1,200 feet AGL, sometimes 700 feet AGL (a faded magenta band on the chart), and sometimes the surface (dashed magenta lines around an airport).
• Class G is uncontrolled airspace below Class E. Most rural drone work happens here.

Getting authorization

LAANC gives near-real-time approval for many locations, up to the altitudes shown on the FAA's UAS facility maps. For anything LAANC cannot approve, apply through FAADroneZone. An authorization is for a specific place, altitude and time, and it may carry conditions you must follow.

Authorization is not a radio call. Remote pilots do not call the tower before takeoff; they get approval in advance.

Common traps

• Part-time towers: when the tower closes, the Class D often becomes Class E or Class G. Check the Chart Supplement for the hours.
• Shelves: under the outer shelf of a Class C, you are not in Class C at drone altitudes. The shelf floor, such as 1,200 feet MSL, is above you.
• Waivers and authorizations are different things. A waiver lets you deviate from a rule such as 107.29; an airspace authorization lets you fly in controlled airspace.