There is speculation that a sabotage plan would have needed help from ground control.
http://mobile.news.com.au/travel/tr...no-sign-of-plane/story-fnizu68q-1226856429922
AS the focus of investigators turns to those on board MH370, a former international pilot has said ground personnel would have been needed to assist in any attempt at a key sabotage theory.
Military radar shows the missing jet climbed to 45,000ft and turned sharply to the west before descending unevenly to 23,000ft on the approach to Penang — on the western side of the Malaysian peninsula. It then climbed back to 35,000ft.
One theory is that this was a deliberate manoeuvre to knock out the passengers and crew.
One Boeing 777-200 pilot, who asked not to be named, said climbing above the plane’s service limit of 43,100ft with a depressurised cabin would have achieved that effect.
But retired United Airlines Captain Gary Brauch, who has nearly 40 years experience on the flight deck including 19 years flying Boeing 777s and Boeing 747s, says the captain would have needed help on the ground.
“My recollection of the aircraft systems is that you cannot shut off the passenger oxygen supply from the cockpit or at all in flight,” he said.
(More at link, I have to cut a lot to keep it under 10%)