Types of Controlled Airspace. Depending on location, controlled airspace may start as low as the ground or as high as 14,500 feet in the United States. With each airspace having varying requirements for pilots and weather, it's important to be aware of classes you might potentially encounter on and flight.

In the United States, "controlled airspace" (Classes A, B, C, D, and E) exists at various elevations depending on the proximity to an airport and the volume of traffic. Class A airspace is the most strictly controlled and begins at 18,000 feet Mean Sea Level (MSL), extending up to 60,000 feet. Near major airports, Class B airspace (shaped like an upside-down wedding cake) typically starts at the surface and extends to 10,000 feet MSL. Class C and D airspaces around mid-sized and smaller towered airports usually extend from the surface up to 2,500 or 4,000 feet Above Ground Level (AGL). Finally, Class E is the general "filler" controlled airspace that often starts at either 700 feet or 1,200 feet AGL to protect instrument-approach corridors for aircraft. Anything below these levels in remote areas is typically "Class G" (uncontrolled), where pilots are responsible for their own "see and avoid" separation. Understanding these tiers is vital for pilots and drone operators to avoid unauthorized entry into flight paths.