Q: iPad Air can't find LTE, only 4G -- on AT&T

I have an iPad Air that runs on AT&T's network. I don't use it nearly as often my laptop and iPhone, so I only just recently noticed that it is no longer finding or at least establishing an LTE connection when WiFi is turned off. As in NEVER does so; it only establishes a 4G connection (judged by both the sense of how fast its internet access performs, and by the 4G indicator in the top left of the screen). Even when my iPhone has great LTE connections and other iPads nearby have an LTE signal. And no city or state spared in all my travels--it just doesn't connect via LTE anymore. I've been wracking my brain trying to figure out when and how this started happening. Best guess I can come up with is that it roughly approximates when I switched over to iOS 9.x. Not fair to necessarily blame iOS 9 without proof, but I can't think of anything else.

Any ideas why this would be happening