Ikarus

 

After a lot of failed space planes sent spiralling into the sky while Jebediah Kerman descends safely to the ground in a detached cockpit, I finally managed to design an aircraft that can go crazy-fast and make very careful turns without going into a spin.

And the higher you climb, the faster it goes - well past the speed of sound, right up until... well, right up until the engines stop getting enough air from the attenuated atmosphere and flame out, putting the plane in a fatal spin.

I made a good bid for the north pole of Kerbin in this kite before finally succumbing to the temptation to go just that little bit higher and faster and dooming the expedition to failure. The worst part was starting to get the plane back under control, just as the engines sheared off.