Originally Posted by bocastephen
Remember - DL has a much higher quantity of domestic FC seats available for upgrade. They fly 762/764/777 widebodies domestically and their 757s have 27 FC seats, while their 738s are 16FC across the board. Even with those numbers, DL Elites are having quite a time trying to upgrade on their own metal with many upgrades being held for gate assignment.
DL loyalists (Medallions) tend to fly DL and not much else - so there is little chance of a 'poaching' benefit where CO could use upgrades as a tool to lure DL customers to become permanent CO customers. All that will happen is mid/low tier CO customers will find their already challenging upgrade chances will go right down the drain and CO could alienate and drive away customers it already owns - not a good marketing strategy.
Additionally CO's 50% EQM policy - reciprocated by DL and NW for CO flights - makes partner flying less attractive. I shun CO flights unless there is no alternative due to the EQM rules.