Which category of airspace requires ATC clearance to enter?

• A. Uncontrolled airspace
• B. Special use airspace
• C. Controlled airspace
• D. Remote airspace

Answer: (C)

The main idea is that ATC clearance is required where airspace is controlled because ATC is responsible for managing traffic and ensuring separation. In controlled airspace, air traffic controllers assign routes and altitudes and issue instructions to keep aircraft safely spaced, so you must obtain clearance before entering to integrate into that system. IFR flights always rely on clearances to enter controlled airspace, and even VFR flights operating there typically must maintain two-way radio communication and follow ATC instructions when required. By contrast, uncontrolled airspace does not require prior approval to enter; pilots operate under their own navigation and visual rules and must see and avoid other traffic. Special use airspace can have active restrictions that require authorization to enter, but if it’s not active, entry is subject to the controlling authority’s rules.