FLIGHT PLAN

I have had some recent fun in developing a spreadsheet based program to generate flight plans for light aircraft.  It is now looking about right but there is still an amount of testing to be done to verify its accuracy.
It has raised numerous problems, the main one was the need to calculate bearings and distances from global grid co-ordinates using spherical geometry and trigonometry.  Then of course there is the problem of converting speeds from Knots to km per hour, and Nautical miles to kilometers, and degrees to radians.
All this has kept me busy in my spare time.