Sensors
There has been discussion of what the Royal Malaysian Air Force (abbreviated to TDUM in the native language) did or did not do on the night when this frustrating, perplexing tragedy began.
A quick look suggests that the RMAF had its radars at Kuantan and Butterworth modernised in 2005 and that two Vera ESM units were introduced in 2007.
There has been mention of RMAF F-16s, only it appears their small but diverse fleet of combat aircraft includes Sukhoi Su-30s, F/A-18Ds and some Mig-29s. As recently as last year a sum of US$100 million was allocated to improving the Su-30s combat readiness from 65-70percent to 80percent or more.
Such data suggests the RMAF takes its role as providing aerial defence and airspace dominance of Malaysian airspace and territory seriously.
One of the characteristics (to which I am of course adding) of posts on this topic is that they come from civilian people based far away from Malaysia so views on what may or may not have occurred within RMAF bases that night are unlikely to be highly accurate.
It would appear, though, that the country does possess the sensors and the aircraft to have responded to a radar track not exhibiting normal identification and not conforming to a scheduled or filed flight plan, although the time to do so would perhaps have provided little opportunity to do so.
Only the country always was and remains relatively narrow, so the timings are always going to be squeezed and presumably the air defence system is rigged accordingly, if only in theory.