The post says:
For the sites that are leaving Beta today, the following criteria were determined:
- [...]
- The site needed to have at least 1000 open questions
- [...]
There is one exception we did make for a community, and that was on the Artificial Intelligence site. [...]
There appears to be another exception: Drones & Model Aircraft has 648 total questions (634 of which are open) and therefore didn't meet the 1000 question requirement.
