I prefer to go on AC from a Canadian destination, rather than other airlines from a Canadian or US destination:
Reasons - 1. I fly on business class and AC (for the cost) has the best business class (at least private pods with flat beds) compared to other Star Alliance airlines going from Canada or USA.
2. I am 200K miles from reaching 1 million status miles - so it is in my interest in flying on AC vs other Star Alliance Airlines.
3. There is the theoretical concern (see my post #46 on this thread:
http://www.flyertalk.com/forum/canad...s-airport.html) that coming via the US will leave me in the nonUS residents' line for customs.
4. If I go to LHR, I have access to the AC arrivals lounge.
However, I guess, esp in the summer, some fares from USA to overseas destinations in business class may be cheaper. But some of the other issues prevent me from doing that.
The one thing I miss when going on AC is not having access to the LH arrivals lounge in Frankfurt - as is the case if one flies on LH, LX, UA, or CO first or business class to Frankfurt. Even if one flies on LH code-shared on AC to Frankfurt, one will not get access to that lounge. However, if one flies on LX codeshared on AC, one will get access to LX's arrival lounge in Zurich (I was able to get access to that lounge on one occasion that way - I had to show the lounge agent not only the boarding pass (which showed it was an AC flight), but the eticket showing it was a LX designated booking on that AC flight).
PS-With the new AC/LH/UA/CO arrangement in terms of transatlantic tickets, has anyone gone on one transatlantic segment on AC from/to Canada and the other transatlantic segment on a nonAC flight to/from USA?