Actually, it's just the opposite. The hijacker(s) would have wanted to maintain radio silence (forgetting to turn off the plane's Inmarsat transceiver was obviously an oversight). Turning on your cell phone violates radio silence. Thus, it argues against the copilot being one of the hijackers and points the finger at the captain or somebody else who knew a lot about triple-sevens.
E.g., perhaps the copilot found himself locked out of the cockpit by the captain. He turns on his phone to send out a mayday, no longer having access to the airplane's VHF. But there's no service. He and others set about trying to break into the cockpit. The pilot depressurizes the cabin, knocking out his tormentors. Then the plane comes within range of a cell tower and the copilot's phone checks in, but its owner is knocked out, so no call is made.
I think that the more conservative bet is found in the Indian article posted at #104 that the “line reattached” as it passed over the island and then just as quickly disattached as it passed out of range with no call being made.
After spending the last 23 minutes at 45000ft without oxygen I’m sure the co-pilot was dead.
And if a call had been attempted there is no guarantee that it wasn’t the pilot using the dead co-pilot’s phone to try to notify whomever — “mission is accomplished”.
Why else would the pilot be flying so low over an island with cell towers unless he was the one who wanted to make an untraceable cell call??? He does everything he can to avoid radar detection but then flies low over a cell tower with 200 cellphones onboard???
Either way this bottom line of the article seems to sum it all up:
“The Malaysian government and media have repeatedly contradicted each other and themselves over details of the search and criminal investigation.”