On WED 6/8 i was flying on DL 1104 from, JFK to LAS, my cellphone was NOT connected to Wi-Fi,in mid flight my iPHONE was in my shirt pocket signaled that a text message had been received, four attempts to respond failed.
I noticed there was one “bar” showing which then disappeared for the rest of the flight.
I was under the impression that cellular only worked via Wi-Fi while flying.