Permission is required.

Think of D as in “Directions” (To fly here you’ll need to receive directions from ATC)

It’s depicted on the sectional with a dashed blue line – – – – -.

• There is an airport with a control tower.
• Usually, Class D airspace extends from the surface to 2,500 feet above the airport field elevation. Sometimes it goes higher. The ceiling is depicted in hundreds inside a blue dashed box. In the example below, the ceiling extends from the surface to 2900 ft [29]. FYI – If the number has a “-” it means up to, but not including. [-29]
• Can we fly over it? Technically yes, but it would probably not be wise. Keep in mind that a motor out would force you to enter the airspace. If you have an aircraft frequency radio AND you understand radio communication procedures, it may be wise to inform a nearby Class D tower where you are and where you plan to go.
• 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.