my longest distance was a 2 hours flight from Geneva to Copenhagen last spring.
While I was doing the math, I discovered a nice function in the new Google Maps which allows you to calculate the distance between two or more points. Just right click >Measure Distance and create your path



So in total I traveled 6888 km or 4280 miles (lol this map is a good example of the pointless things I do when I can't sleep at night, it's 4AM here).