Kilimanjaro and Dar Es Salaam are international, Arusha is local only and the main hub to just about any and all destinations throughout Tanzania, if you’re on safari, odds are you will go through there at one point or another. The airport itself is more or less within the confines of the City of Arusha, depending where you are give yourself 20 to 30 minutes to get there, if you’re in town or one of the hotels in the surrounding neighborhood. There’s not much at the airport itself, basically a really long strip of tarmac and a few very small buildings dotted about which serve as the local offices. The “terminal” is more or less open air. There are a couple of stalls to get coffee, a snack or a soft drink. If you consider that most travelers are getting on to small planes and jumping between local airstrips the scene at Arusha Airport is pretty chaotic. Lots of bags and bustle, although oddly enough it seems to work well enough and you will end up getting on your flight.
Tracking flights in and out, while it may be possible, it’s not easy, and trying to find someone to call about your flight really isn’t going to happen, so make sure you get there on time.