From the AA day-pass FAQ"


Q: Is the pass is valid for connecting flights?

A: If you are traveling through different cities with lounges, you can use the day pass to access more than one room that day. If you are traveling overnight, the pass is also valid at the first point of arrival the next day. * Please note that due to restrictions on the airports themselves, may not have access to Admirals Club of Canada, Europe, Asia Central and South America located past the passport control.