I have heard stories about those Airport tournaments!
It's been years since I was involved, and you are technically right about ACHA M1...However, way back before there were women's teams in the ACHA, they were officially referred to as divisions and therefore D1, D2, and D3. This is years ago since I was involved, so yes, I'm sure you're right the names changed, but there are probably other older people like me still saying D1. This link is to the ACHA website from 2005 - notice they say D1:
http://www.itsportsnet.com/league.php?scriptName=HOME&leagueID=7700