Airspace — the simple picture

The sky is divided into boxes

Above every airport there's an invisible box of controlled airspace. You can't fly through it without asking permission from ATC first.

Outside those boxes, the sky is mostly uncontrolled — pilots are responsible for spotting each other and staying apart.

Why the boxes exist

Airports are where aircraft bunch up. At 200 kt closing speed, two aircraft can be a minute apart and still collide. Controlled airspace means one person is in charge of who goes where, and everyone does as they're told.

Prestwick's box

EGPK has a box that:

• Starts at the ground
• Extends roughly 15 miles around the airport
• Reaches up to about 5,000 feet before becoming a bigger box above

If you're flying anywhere in that volume you talk to Prestwick Approach and do what they say.

Why this matters to spotters

When you see a small Cessna with an odd callsign flying overhead, and you hear it being told "VFR transit via Ailsa Craig, maintain 2,000 feet, QNH 1013" — that's an aircraft asking permission to cross the Prestwick box and ATC granting it.

Ready for more

Read the full airspace lesson for the ICAO class system, the Scottish FIR and the difference between Class D, Class G and everything in between.