More specifically when the user clicks on a specific point on the planet and moves the mouse cursor you want that point to still be under the cursor when the mouse button is released. You can extend this construct outside the central sphere into a camera control that works across the screen and feels very intuitive at any zoom level.
Google "sgi trackball" for some interesting code to point the way.
The travel time between any 2 airports is random and increasing the speed value just makes that random value smaller in general. I liked the way it looked at fast and slow speeds so I figured it was worth adding an option.
Ha! Look over the Bermuda Triangle :) Colors is a really good idea and I experimented a bit with changing colors based on direction E/W and N/S - I like the idea of using velocity though and since it's not scientifically accurate, estimating based on position within the arc is probably good enough.