Categories 2 and 3 open flight over people to heavier aircraft than Category 1 allows, and they share one structure that differs by a single number. Each requires that the aircraft will not cause injury equivalent to or greater than the severity caused by a transfer of a set amount of kinetic energy on impact from a rigid object — 11 foot-pounds for Category 2, and 25 foot-pounds for Category 3 — and, on top of that threshold, that the aircraft has no exposed rotating parts that would lacerate skin and no safety defects. The kinetic-energy figure is the heart of it: it caps how hard a blow the aircraft could deliver to a person underneath, and the higher 25-foot-pound ceiling is why Category 3 comes with tighter operating limits than Category 2.

You do not measure any of this yourself — the manufacturer proves it and the FAA accepts the proof. The demonstration runs through a means of compliance under § 107.155: a procedure of test, analysis, or inspection that the FAA has accepted as a valid way to show the aircraft meets the Category 2 or 3 requirements. Using an accepted means of compliance, the manufacturer then submits a declaration of compliance under § 107.160 — a record naming the make, model, and serial numbers, identifying the means of compliance used, and declaring that the aircraft meets the threshold and carries no safety defects. Once the FAA accepts that declaration, the aircraft is listed as eligible and must bear a permanent, legible label stating its category. As a remote pilot, that label and that declaration are what tell you an aircraft is qualified.

Two duties then fall on the remote pilot in command. The first is the label itself: under § 107.135, if a Category 2 or 3 label is damaged, destroyed, or missing, you must re-label the aircraft — in English, legible and prominent and durable for the whole operation — correctly identifying the category before you fly over anyone. The second applies only to Category 3, which § 107.125 fences more tightly: a Category 3 aircraft may never operate over an open-air assembly, and may be over a human being at all only within a closed- or restricted-access site where everyone has been put on notice, or without sustained flight over anyone who is not participating in the operation or sheltered under a covered structure or stationary vehicle. Category 2 carries no such location limit — the safer, lower-energy category is trusted with the freer operations.