I thought the en banc request had to come down within 30 days of the ruling? It must be close to a year since Peruta
No, it turns out it is quite a complex process. In the end, any one judge may ask for an en banc hearing sua sponte. Then the judges vote on it to decide.
The sua sponte call only came after the call for intervention to allow Kamela Harris to intervene on an en banc hearing was denied through the normal process.
Here is a graphic that shows the process of the sua sponte vote:
http://gunwatch.blogspot.com/2014/12/sua-sponte-process-for-en-banc-in.html