Chapter 1 established the basic bargain: some airspace is controlled, and controlled airspace requires permission before you fly. § 107.41 is the rule that draws the exact line. It says no person may operate a small unmanned aircraft in Class B, Class C, or Class D airspace, or within the lateral boundaries of the surface area of Class E airspace designated for an airport, unless that person has prior authorization from Air Traffic Control (ATC) — the service that sequences crewed traffic around airports. Everything in this chapter about getting authorized flows from that one sentence. Notice what it does not do: it does not require authorization everywhere. The names it lists — Class B, Class C, Class D, and the surface area of Class E designated for an airport — are the entire list. Airspace that falls outside those designations is uncontrolled, and § 107.41 asks nothing of you there.

Classes B, C, and D all exist for the same reason — each wraps the airspace around an airport busy enough to need active control. Part 71, the regulation that designates airspace, defines all three as areas built around at least one primary airport. They are not managed equally tightly. § 71.41 places Class B under the most demanding set of pilot-qualification, operating, and equipment requirements; § 71.51 and § 71.61 place Class C and Class D under operating and equipment requirements that step down from there. Those distinctions govern how crewed traffic is handled inside each ring, not what a Part 107 pilot must personally hold — for a remote pilot the bottom line is identical across all three, and it is the § 107.41 requirement: get prior ATC authorization before you launch.

Class E is the class that catches people out, because most of it is nowhere near the ground. Under § 71.71, much of the country's Class E begins 700 feet or more above the surface where it supports an airport's instrument approaches, or 1,200 feet or more where it transitions traffic to and from the en-route structure — all of it well above the 400-foot ceiling a drone flies under, so it never enters your picture. But § 71.71 also provides for Class E designated for an airport, and in some places that airspace extends down to the surface. That surface-area Class E is exactly what § 107.41 names: fly inside its lateral boundaries and you need prior ATC authorization, even a few dozen feet off the ground and even if there is no control tower in sight. The takeaway is that you cannot judge airspace by whether you can see an airport — you have to read what the airspace over your site actually is, which is the next section.