My Experience With Delta Companion Upgrades
One of the benefits as being a Medallion member with Delta is the Complimentary Companion Upgrades. You and a traveling companion may both enjoy First or Business Class cabins when traveling on Delta and Delta Connection carriers, if there are empty first class seats after all other Medallions are upgraded.
Your traveling companion must be a SkyMiles member and traveling on the same flight. Companions are cleared no sooner than 24 hours in advance of departure and both the Medallion member and companion must be booked in a revenue class of service. If the Medallion and companion are booked together and are on the same reservation, both upgrades can be requested online - otherwise you have to call to have it done manually.
Delta Upgrade Priority Chart
To Book Together or Not?
If you are on the same reservation as your companion, your upgrade priority will drop to the companion window (24 hours), pulling you down behind all other Medallions. In my situation, I am a Platinum Medallion, so I normally clear 5 days out - and on the route I was booked on (LaGuardia to Miami) upgrades are all but certain for Platinums.
However, my companion did not have status and had to check two bags (long story). If I booked the tickets together, she would get free checked bags since the Medallion free baggage benefit extends to up to 8 other people on the same reservation. However, if we booked together, I risked potentially losing out on my upgrade and both of us would be relegated to coach, though with free bags and SkyPriority.
If I made separate reservations, or split them, I'd almost certainly clear at my window, but my companion would be left up to the upgrade gods and would potentially have to wait until the gate to get the upgrade. In the latter case, she'd have to pay to check bags (unless a check-in agent was sympathetic and waived the fee since they technically should have bags waived if not for the negative upgrade effects). Two bags would cost $70, unless of course her upgrade cleared in advance and as a first-class passenger she'd get 3 bags for free.
So I decided to roll the dice and made separate reservations and called Delta to request the companion upgrade within 20 seconds. The upgrade gods were looking positively at me this time around, because my upgrade cleared at my Platinum Medallion window and my companion cleared at 35 hours before departure - and they automatically assigned us next to each other, which was nice, though I'm not 100% sure if it was done on purpose.
I thought this experience was nifty enough to share, since I used to think companion upgrades would drag down the Medallions' upgrade priority no matter what. However, there are some limitations, such as, companion upgrades must be requested at least three hours before the scheduled departure of the flight.
So sadly, if you see a hottie at the gate and want to impress them with your Medallion prowess, you'll need to do it at least 3 hours before scheduled departure - and who really gets to the gate that early before a flight these days? However, if you are flying with colleagues or friends, you might as well list them for the upgrade - unless of course you don't want them to be in first class!