Although none of the radar sytems (except maybe China and Taiwan?) are cutting edge. Rivals can determine their capabilites by the signature of the broadcast signal. Odds are these are off-the-shelf units from well-known systems makers in the USA, Europe, or Russia.
Some interesting thoughts here.
My presumption that the airliner could escape radar systems was based on the fact that this missing flight seems to have flown out of the range of the systems, over open water. Once over open water, one could get anywhere within fuel range. Perhaps a spec of an island somewhere? How flat does a runway need to be for one of these- could a well constructed dirt runway handle it? I suppose an operation like this wouldn’t likely have the resources to construct a paved runway, but in some of the nether-regions of the world maybe that isn’t so expensive.
As for reasons, two that don’t seem absurd to me are ransom, and N. Korean shenanigans. After all, they have stolen Chinese trains before.
That should work but you are going to have to fly really low not to be picked up by radar. You would have to stay at less than 500 feet or so which isn’t a good altitude to fly an airliner. I don’t know if their autopilot will even allow an altitude setting that low. Even if it does, range is severely diminished because of the much thicker air at low altitudes. True ground speed would also be fairly slow (200 knots or so). You wouldn’t be stealthy at all because anyone that you happen to pass over along the way will instantly notice that a huge plane is flying really low and slow over them.
You could fly a low and slow course until you get far out to sea and then climb to normal altitude again. As long as you turned off your transponder or programmed it to send a bogus signal, there wouldn’t be any way for controllers or radar returns to know who you are or where you originally came from. You might be successful at that point if you had a country that wanted to cooperate and provide a suitable airport.
Not theft but depending on your point of view, aircraft repossession without permission is close. Here is an article about that business.
What a great article, thanks! 
Er, what? Really? I mean, I know they kidnapped that filmmaker and forced him to make Pulgasari, but how?
I wonder whether there was anyone on the plane of interest to North Korea…
Another known case of airliner theft was Iraq’s invasion of Kuwait.
They disguised it and kept it out of reach until a Haj (pilgrimage to Mecca) caused them to leave it on the ground in Saudi Arabia, where they got around to checking a serial number the Iraqis either did not know about or figured didn’t warrant the trouble of changing.
There wouldn’t a market for it.
Each of the major components on airplanes is logged down somewhere, so even if you were able to steal it,fly it to a remote area undetected and then repaint it, the parts all have serial numbers which correspond with a certain plane.
Also, planes such as 777s require very specific maintenance schedules to remain airworthy. That means that whoever purchased the stolen aircraft (assuming the object was to sell it) would have to have a number of highly trained aircraft technicians on staff with a great of expensive tooling and years of experience. You couldn’t just fly it back to the Boeing plant for a “tune up” if things started acting up.
Finally, large jet airliners require lengthy improved runways. You could set it down on a jungle dirt strip, but you probably are never going to get to take off again. And any sizable airport within the maximum flying range of plane would notice if a 777 just turned up one day. Especially one whose tail number has likely been transmitted around the world.
Here’s an article about the stolen trains.
I also heard a story (possibly the same incident, but I can’t find a specific site for it) where the Chinese sent in some trains with aid on them, and NK refused to return them saying the trains should be part of the gift. Now that’s some brass balls- shouldn’t it be up to the giver? Imagine going to a dinner party, bringing a cake, and having the host tell you that surely the cake plate is part of your gift.
That link brought up a registration agreement. When I closed it, I got the current front page.
quote:
October 18, 2007 11:06 pm
China halts rail freight to N Korea
By Anna Fifield in Seoul and Richard McGregor in Beijing
China suspended key rail freight services into North Korea last week after 1,800 wagons carrying food aid and tradeable goods crossed into Kim Jong-il’s hermit state but were never returned.
Goes on to speculate that the KN was selling the cars back to China - as scrap metal.
But even for the current loon-in-power, stealing a plane with 200+ passengers on board would be unnecessarily messy. They have freighter which make routine trips to Singapore (IIRC) for luxuary goods for the elite. Having a spare flight crew on board and losing them at a busy terminal would seem a much neater was of grabbing one.