I've been using TripitPro for several months now and use it as well as Flighttrack which gets a feed from Tripit. I canceled my "pro" membership and my account changed immediately back to the non pro. I the installed the Amex app and linked back to Tripit and my membership changed back to TripitPro.

The app instructions are not very clear but it's working like a charm. I like the seat advice - saves a separate visit to seatguru