Plus don't forget tax exemption due to combat zone visits. That can pay off quite well. I think they're guarding against the folks that used to take a 2-day TDY to the 'Deid on the last day of every month so they could get the full year tax free in return for 12 2-day TDYs to Qatar (Qatar also no longer gets tax exemption IIRC), but trips to xxxistan or other actual nasty places still pay off with a couple of small allowances and a tax exemption, that can total up to $1000/month or more. Heavy drivers may have much greater opportunity for these trips than fighter or support folks.