[cynwoody]

ACARS sends data ONLY on significant events (gear-up, gear-down, achieving cruise) and NEVER on time. So the reports that it sent out data every half hour are wrong - it would not be expected to send out more data until gear-down (which didn’t happen).

Reportedly, they turned off ACARS first, before the transponder. What they neglected to do, however, was also to turn off the satellite radio system that ACARS uses. It pings the geosynchronous satellite from time to time, even if it has no traffic, and the satellite is able to gauge the airplane's distance, but not its direction, from the ping timing. That is what those circular arcs on the map are based upon.

[robert14]

Hello cynwoody. Please read post 47 in today’s Sunday Talk Show Thread 16 in the right side border. Post 47 and the following posts should answer your questions.

[Izzy Dunne]

Reportedly, they turned off ACARS first, before the transponder.

But, if the expert friend if right, the ACARS wasn't necessarily turned off. It wouldn't have transmitted until something significant happened.