Uh now physics isn't my favorite class but I seem to recall that the teacher said something about speed of light once(I was playing Alpha Centauri so I didn't hear it all).

When person 1 approaches the speed of light for an external observer, person 2, person 1 would approach the speed of light at a slower rate than person 2 percieve it. So when person 1 actually reaches a velocity of the speed of light person 2 will percieve it as a speed higher than light.

I can't remember the details but I think that was it