So I was looking into this following the instructions at http://sourcefabric.booktype.pro/airtime-25-for-broadcasters/upgrading/ (we installed via the automated installer on Ubuntu using apt-get) and the command to upgrade (apt-get update and apt-get upgrade) does not list Airtime as having an update available. I confirmed this by looking at the source repository and it's still listing 2.5.1 as the most recent there (http://apt.sourcefabric.org/dists/trusty/main/binary-i386/Packages). It looks like even though they've made 2.5.2 available they have pushed an automated upgrade to the Ubuntu channels yet. There isn't any guidance on how to update it outside of using the automated installer so I'm afraid I can't be of much help, but at least this explains why it's running the previous release even though we just installed it a little over a month ago. Hopefully they'll push the update to all server repositories soon, maybe they're having issues with it and don't want to release it just yet to the automated channels.