I've been using Priority Mail 2-Day Service from the US Postal Service, and its flat rate boxes, to mail supplies to my thru-hiking husband. Everything went OK with the first few deliveries, probably because I mailed them early, but when he didn't get his scheduled delivery today, I called USPS to see what's up.
Apparently their Priority Mail 2-Day Service can take up to 5 days for delivery, AND, it is not guaranteed. The only service that is guaranteed is Priority Mail Express 2-Day.
I have written to the USPS Consumer Affairs Office in Washington DC to complain about this deceptive advertising.
But I also thought I should let people in the hiking community know, in case they are using this service to get their scheduled supply packages. I think it will be OK if you allow extra time for delivery; but if you have a critical package you need by a specific date, it might be better to use the guaranteed service.
_Lovely Laurie_