What do the numbers inside the dots on the map mean

It is possible for a higher-level player to gift you the parts to build a plane that you haven't yet unlocked.

However, I think this image is just a developer version of the app.

The colors are used to tell which class the airport is, there are 3 classes:

• class 1 (black)
• class 2 (blue)
• class 3 (red)

The main difference is related to where an airplane of a specific class can land: an airplane of class 2, for example, can land just on class 2 or 3 airports.

Once you get a class 2 airplane, you'll use the colored dot on the Jobs screen as a handy way to spot jobs that can go directly to another Class 2 (or better) airport so that you maximize the effectiveness of your Class 2 plane.