Originally Posted by mia

To make a meaningful comparison I think you would need to look at availability through Continental and Delta on the same dates.

To take the JAX-LHR example there should be one-stop service:

via ATL on DL
via DFW on AA
via DTW on DL
via EWR on CO
via IAD on UA
via MIA on AA
via MSP on DL
via ORD on AA or UA
via PHL on US

I based this on a list of nonstop destination from JAX published here, and my recollection of who flies non-stop to London from various markets. Accuracy not guaranteed .

Aeroplan should have access to flights operated by CO, UA, and US. You might try checking availablity for each segment separately to verify that their site is constructing the best connections.

Also, AA and B6 (JetBlue) have a partnership which might allow you to fly to BOS or JFK on JetBlue and then internationally on AA, but I do not know if this partnership extends to award redemptions.