I'm starting to think that also.
I was being stupid saying that the air force might have been present because then they'd know where the plane is.
A lot of this isn't adding up though.
To answer your question about visibility of the aircraft to tracking systems (and excluding military-capable ground, sea and satellite systems), it's on the previous page
The thing with radar contact / vhf sight is that you can go to low altitude to evade that and therefore become 'invisible'. However, the plane is unlikely to have exceeded 2,500f/min descent and would have taken nearly 15 mins to achieve the required altitude.
Whatever altitude it was at the telemetry transmissions (via SATCOM, line-of-sight-to-ground not required) should have continued. They didn't, the logical conclusion seems to be that they were deliberately terminated (unlikely but not impossible) or that the aircraft was suddenly destroyed.
Since I wrote that I'm starting to wonder how many of the auto transmissions
were made and how complete the public information is. If it
isn't complete then I'm sure that's for a very good reason.
One theory on Reuters and AP is that one of the passengers may have taken a large insurance policy or similar. I immediately thought they'd taken a leaf out of this thread's book and started working through mini-series/disaster-movies looking for clues...
EDIT: It's believed it
was flying without emitting any transponder or otherwise and was spotted at around 30,000ft (5,000ft lower than its planned cruising altitude) by military radar over the straights of Malacca, about 150 miles off course.
That's not to say that it got much further than that, but this is becoming stranger and stranger.
The plane crossed back over Malaysia and headed out to sea without trying to make land or descend significantly, despite having an issue that rendered the transponder and radios inoperative. There must surely have been some human mal-intervention?