I want to add more to what Anwar is saying:
http://www.nzherald.co.nz/world/news/article.cfm?c_id=2&objectid=11232602
There is much more detailed info here about what equipment Malaysia had purchased, but too much to quote so here is the gist:
http://www.malaysia-chronicle.com/i...-to-human-lapse-not-radar-incapacity&Itemid=2
But I can kind of see that it would have just been another blip on a whole screen of blips, YKWIM? And like the other official was saying in the link posted upthread, it was not coming in from outside into Malaysia. So I can see how they would not see it as a threat. Also, it was in a confusing zone, where maybe they thought Thailand was covering that plane on its radar, and since it was on a commercial flight path, they probably thought, no big deal. That was the whole point, IMO, of whoever was flying to go along the ATC border lines.
It does serve as a wake-up call though, for probably every single country. They need to make some changes, obviously, in how these planes are tracked on the radar screens, and how to determine exactly which country is tracking the plane.
I am not sure exactly how the radar and air traffic controls work. But for example, could they not "tag" planes to show someone conciously has it "under watch," and then the blip shows up color-coded in a certain color after its been tagged? Then whatever blips shown on screen that are in a different color, means no one is "watching" that plane.
For example, Malaysia Air control "tags" 370 as its flying northeast towards Beijing. Let's pick a color, say Red. So the blip shows up as Red on everyone's screens who can see it. Then, when it gives the command "370, please contact Ho Chi Minh City," then it "untags" the plane. So the blip reverts to "untagged" color, let's say Green. So now the blip is Green.
When Ho Chi Minh takes over the duties of watching the plane, it "tags" it Red. The blip goes back to Red to show that someone is conciously keeping track of it.
In this case, Ho Chi Minh never got a hold of 370. 370 never contacted Ho Chi Minh. Malaysia had already "untagged" it, so it shoudl have showed up as Green on any country's radar screens (like Thailand and Malaysia).
So now, 370 is going back across Malaysia, and it's also being picked up by Thailand's air space. In both of those screens, it's going to show up Green. Meaning no one is watching it. So immediately, Malaysia would see that something is wrong. Thailand would see that something is wrong. Thailand woudl contact Malaysia - hey do you see the Green blip? What happened?
Malaysia, says I don't know. Malaysia then goes and checks with other countries' ATC, like Singapore and Vietnam. Says, hey do you have a plane that hasn't checked in with you?
Anyway, they would VERY SHORTLY figure out they need fighter jets up there to check out this Green untagged blip.
JMO.