Air Force - Can the PT jacket be left unzipped when worn?

Provided that I'm by myself and not a part of an organized PT in a unit, am I allowed to wear the PT jacket unzipped? I looked at AFI 36-2903 and it clearly stated that it can be zipped or unzipped when worn, but it was dated 2006, which was a whopping 5 years ago. A lot can change to regulations in 5 years, so I was wondering if anyone knows for sure what the rule is. Even better if you can show me where to find the official, up-to-date documentation that says so.