Why does a roller ball type pen sometimes leak while in flight or at high altitudes and how can I prevent it from happening?

Roller ball pens have a thinner ink than typical ballpoints. This type of ink provides a smoother, more consistent write, much like a fountain pen. The problem of leaking may occur when consumers have a newer pen and take it to an extreme air pressure (such as in a plane). If using roller ball type pens in high altitudes, equalize the pressure by taking the cap off with the tip facing upwards. This allows air into the chamber without pushing the ink out of the tip. Most recently, uni-ball has introduced the Vision Elite – the smooth-writing roller ball pen that is guaranteed leak-proof in flight.