There are some rare occurances that cause the distance and airtime to go crazy. For example, when killed by a hurting poly, I got a very weird airtime number. Maybe you could have airtime show up only when the player is killed by a weapon?

Here's a screenshot. :)

Hmm I tried letting myself die on hurting poly's, at my own server.. The air time remained 0 every time. Perhaps that was just a freak server sort of bug. Like when the scores sometimes turn into 64545334 .. Know what I mean?

It was happening for both of us, and we were on a dedicated server (we weren't hosting).

Also, occasionally when I /kill, it says Distance: -0.1m