Howdy folks, I'm trying to figure out why one leg of my flight was upgraded to Y for which I received a bonus .5 EQS and 50% EQM bonus for the leg. I tried to search but was unable to get meaningful results. Here are the details for the ticket. I'm hoping to understand what happened so that if it is something I can effect in the future I plan accordingly. About me: UA/CO 1P/Gold Elite Purchased Itinerary: One-way, all (3) legs in K class, with same K**** booking code. Reservation made on .bomb. (3) legs - CO/UA/UAx metal. Reviewing my .bomb Mileage Plus account summary the following credit appears: Leg 1 - CO metal, I was UDU to F, earned normal EQS/EQM, earned 100% "bonus for elite members", fare class listed as K. (This I would expect is normal behavior) Leg 2 - UA metal, I was UDU to F, earned 1.5 EQS***, earned normal segment miles, earned 100% "bonus for elite members", fare class listed as Y***. *** So I earned a .5 EQS bonus, it was upgraded to Y and where this gets weird is I also earned a 50% bonus for that segment's miles but they were not listed in the "bonus for booking code" area for that flight's credit but rather appeared by an increase in my "Bonus for promotions and booking codes" section. There is no corresponding entry in "My activity details" for the bonus, it just appears in the total balance for that section of my YTD EQM. Leg 3 - UA Express metal, earned normal EQS/EQM, earned 100% "bonus for elite members". (Again, normal expected behavior). What I'd like to know is why this happened and if there is a way I can get it to happen more frequently. 1. There were no registered promotions I am aware of that would have given this result. 2. I maintain a notebook where I break out EQM earnings in three sections (UA/UAx; partner airlines; bonus for promos/bookign codes) and to the mile that is accurate. There is a chance that it could have come from another activity such as United Visa, United Shopping Mall or another promo but highly unlikely because is was exactly 1//2 of the miles for that segment. Plus the fact that I also got a 50% bonus on the EQS makes me think they are related. Any insight would be greatly appreciated; PMs welcome too. I didn't want to call UA MP for explaination for fear of it getting recognized as an accidental credit.