Originally Posted by
Kacee
Quite the opposite: UA calculates domestic upgrade prices based on the differential from Y to F. This can sometimes result in a discount to the current F fare because it calculates based on the theoretical difference rather than the actual differential.
Not my experience. Here are a couple fare differentials on DTW-MSP (L and T fares) from EF. The $80 and $90 seat upgrade offers (total $170) did not match the $130 fare diff (which can't be split across segments due to being single fare component).