Permission is required.

Think of C for “Caution” (It’s busy enough that you need to have caution)

It’s depicted with a solid magenta line on the sectional chart

• It’s also shaped like an upside-down wedding cake but it’s a smaller cake than Class B.
• There’s an airport with a control tower.
• Can we fly under it? Yes, but you’ll need to stay in Class G or E and avoid flying over congested ground areas.
• Can we fly over it? Technically yes, BUT it’s still a very bad idea because a motor out would force you to descend through the Class C airspace.
• We CAN’T fly here without special permission from ATC. Permission should be obtained in advance by telephone (some controllers will accept a radio call).
• IF you enter (assuming you have permission), you must remain 500 ft below, 1000 ft above, and 2000 feet horizontal of clouds AND must have 3 miles of visibility.