Phone calls
How is it passenger phones were still ringing what at least 6/7 hours after taking off and leaving cell service? Surely this means phones are on and still within range of a cell tower. I have a very wild theory but unsure if it is entirely possible but certainly sure at a government/military level could be possible. Which is why the early days are very shady from Malaysian authorities as they did not expect this to be worldwide news within hours of its expected arrival time in China, yet things suddenly become clear as other authorities get involved