The Miles card gives up to $ 30 a year for inflight WIfi purchases, a benefit I cared about not at all (at least compared to the 3% cashback!) Just looking over my last statement though, I see a $ 25 credit and a $ 4.99 credit for inflight wifi.
I was pretty sure I didn’t use it, and looking more at the actual charges (and the details are on the Discover statement!) , the $ 25 was first checked bag, the other was some inflight snack. So, the credit is useful, much wider than inflight Wifi!