I've been experiencing full connectivity on every Alaska flight for last year. My phone has T-mobile plan that allows direct connections. There is traffic shaping but it's easily bypassed by the VPN and voila, everything is available, youtube, telegram, whatever. It's not that amazingly fast but works. I bet I could do a voice call if I wanted to. But I won't do it because it's not polite to neither my neighbors nor person I'd call.