I know from a friend that sometimes pilots communicate with HAM radio frequencies. Just to kill the time, just for pure fun. It happens -for example- when they flies to Africa. Over long stretches there is no other communication than Satcom or RF radio, that's it. So for the Malaysian 777 you can think of the same scenario: Only Satcom and a beacon frequency, detected and responded by radar. The latter has been switched off.... Scary.... !!
ACARs was upgraded from something like 2400/4800 baud to 33K-baud in the late 1990's -- to about 2005 -- it only works within about 120-180mi of the land based ground station - after this depending on what the airline has paid for and what unit's are powered on in the aircraft the data is re-routed via SATCOM -- as this airliner normally only flew shorter distances over water, and the airline was under-water financially it might not be that un-common for the SATCOM routing to be turned off in the aircraft configureation. As more than one ACARS transciever is normally carried, and the data stopped all at once it might be the case they were switched off.
There was a discussion going on this subject on the news channels yesterday eveing and one of the panelist told that no one will ever come to know about what happened to this airline. He was saying since 1948 there are 82 planes that went missing and there is no data found on what happened to them and this is going to be the same case.
@Max: As I have learned from the recent discussions, ACARS (Aircraft Communications Addressing and Reporting System) does the same kind of communication that you have mentioned. But I am not sure, when that system was last modernized. I understand in the aviation industry technology progresses at a slower pace as the "proven-in-use" technologies are adopted and newer stuffs goes through a lots of certification process to analysis unless the failure-modes are well defined and proper preventive & protective measures are taken. But this kinds of incidents drive us to re-think: could we improve anything?
I'm actually not so surprised, in cases where the plane is flying over an ocean. The only long range link that works in cases like that would be satcom, but there's no guarantee that the entire oceans are continuously covered. Over land, and even on crossings between North America and Europe, airliners should almost always be within range of some ground control. But the southern hemisphere has gymongous expanses of ocean.
Most of the planes put in service after 9-11 have a few more systems that provide more data at a higher data-rate -- this system was put in service in the early 1990's and if I could remind everyone in that era GSM with 9600 baud data was the norm for cellular even - a big issue is that airlines around the world are strapped by high fuel costs, and unless the system that provides tracking can also be leveraged to reduce this expense in daily operation, there is no ROI to allow for upgrades.
I must admit that I find it hard to believe that, with all of the technology available to us today, we can completely lose track of a 777 airliner for goodness sake!
I think one problem is that a lot of the systems we engineers designed originally were not created with the thought of malfeasance in mind. Having said that, since the 9/11 infamy, I would have thought it would be mandatory to equip aircraft with something that kept on transmitting its GPS coordinates every minute or so and that could not be disabled from within the plane itself.