adk
Steals Hotel Toilet Paper
I switched from T-Mobile to Verizon when getting the new iPhone specifically for coverage reasons. In major cities T-Mobile worked fine, but in between and in some smaller towns there was little coverage. Plus coverage indoors was pretty poor. I still would prefer T-Mobile from a company and plan point of view, but almost being stranded in Arcata, CA unable to call FSS to file an IFR flight plan because of a missing payphone made the decision for me.
Now for international, T-Mobile was definitely better.
Was going to say the same thing. T-Mobile is great in big US cities and in most places internationally, but in smaller US cities coverage can be weak. Since you're doing 135 I'm guessing you'll be spending a fair amount of time in places like Paducah, Pueblo, Pocatello, and Preque Isle ... Something to consider.
I have no international plan, and it's really only an issue going to and from the hotel. Almost every airport I've been to outside of the US has very good free wifi, and most of the hotels American crews stay at have good wifi. If you'll need to be able to speak to your company on your cell phone at any given time T-Monile might once again be a decent bet.
PS - welcome back!