Australia has agreed to help Malaysia searching the southern 'arc of possibility' for the missing flight 370. If the captain went nuts and decided to end it all, that's likely where the wreckage will be, a couple of miles down on the floor of the Indian Ocean. Most of the interesting conspiracy theories would have it somewhere along the northern arc, however, landing on a smuggler's strip in South Asia.
This Guardian piece has an interesting couple of pars on Australia's air defence net, which has an extensive surveillance reach to the north, especially along the Indonesian Archipelago. About three thousands miles, reach, probably more. (3K is only what's acknowledged on the record).
What I found interesting is how quickly any cover dies when you track northwest and west, however:
There are just two primary radars on the West Australian coast, one in Perth and one further north in Paraburdoo, which has even less range and is used to monitor mining traffic heading to the nearby Pilbara region.
Australia’s Civil Aviation Authority relies on aircrafts’ automatic dependent surveillance broadcast to ping information to commercial satellites, such as telecoms firm Optus’s four telecommunications satellites, and back to ground control.
The source said that this was the case with flights by Emirates Airlines, which all fly over the Indian Ocean to Australia, but it did not provide a specific radar plot.
Australia does not have any government satellites.
The Australian military has an over-the-horizon radar network that allows it to observe all air and sea activity north of Australia for up to 3000km. This encompasses all of Java, Papua New Guinea and the Solomon Islands.
Although the Jindalee operational radar network extends part-way across the northern Indian Ocean, government papers online describe it as a “tripwire” in Australia’s northern surveillance system, helping underpin the defence of the country from any attack originating from the north.
Given the Chinese PLAN's intention to develop a blue water fixed wing fleet air arm, that big yawning blank spot on the map over the Indian Ocean suddenly doesn;t look so empty. Money on the barrelhead it gets filled in by an extenstion to JORN sometime in the next four to five years.