We often fly through Charlotte, and when I have to go through Charlotte and there is a 35 on 40 minute connection time, I can usually find an earlier flight from my local airport to CLT to give me more than 35 minutes than the default selection that comes up when you search for a flight from your local airport to SXM. While arrival times are usually padded a bit late ( meaning the time the plane usually arrives prior to the published time ) it can take a fair amount of time for the plane to taxi to the gate, then to get off the plane, and then there is the time to determine the gate for the flight to SXM and then getting to that gate. On top of all that, AA says they have the right to close the cabin door 15 minutes prior to scheduled departure. That means if the plane actually gets to the gate 35 minutes before the SXM flight takes off, that would be cutting it pretty close.