An FAA sectional section

Is this due to years of looking at CAA charts? Who knows. If you look on the example fragment of a sectional you’ll see an airport depicted. This is the magenta circle with bumps at the 3pm, 6pm, 9pm and the midday positions. The white line indicates the rough orientation of the runway. The fact the the circle is filled in indicates that is is a hard runway with a length between 1500 ft and 8069 ft. The colour magenta for this airport indicates that it does not have a control tower. If it were blue then the this would indicate that it did have a control tower. The tick marks around the outside indicate that services are available during normal working hours. What constitues normal working hours is accurately defined in the Airport Facilities Directory, but by default means 10am until 4pm Monday to Friday.

If the airport runway is outlined in solid color with no circle around it then this is a big runway (greater than 8069 ft. Seabases are shown with the magenta anchor inside a circle (the one on the chart, without a circle indicates it is for Emergenct seaplane operations only).

Abandoned runways are shown in the same way as on CAA charts with a cross through them. Strangely enough they are all magenta in color.

Military airfields are shown with a double circle either with the tabs around them, indicating they are civil / Military or withour indicating, you probably shouldn’t land there unless you’re flying an F-15.
Airfields with an “H” inside the circle indicate heliports. Aerodromes with a “U” inside the circle indicate “Unclassified”, i.e. Area 51 or aliens please land here. An “F” indicates an “Ultralight Flight Park”.

That’s about it for the actual symbols. Next time we look at the numbers which can be written in the vicinity of the aerodrome. There’s a lot of those!