Deputy Commander of Vietnam 918 Air Brigade Senior Lieutenant Nguyen Tri Thuc looks out for the missing Malaysia Airlines flight MH370, that disappeared from radar screens in the early hours of Saturday.

How is it that we have no idea where Malaysia Airlines flight MH370 has gone? The answers offer a humbling look at the limitations of technology, says Brian Fung.

Washington - Call 911 from the side of the road and GPS satellites can tell dispatchers exactly where to send help. Airline passengers have access to detailed maps that show precisely where they are during their journey. Hop onto wi-fi, and somehow Google knows whether you’re logging on from Lima or London.

For all these abilities, how is it that we have no idea where Malaysia Flight 370 has gone? The answers offer a humbling look at the limitations of technology.

What happened to radar?

Radar only extends so far. Most of us landlubbers understand air traffic controllers use radar to monitor a flight’s progress. That’s all very well over land. But radar also has a limited range, and you can’t put a radar station in the middle of the ocean. So pilots often have to stay in contact through other means, such as periodic radio check-ins. In between check-ins, the controller has only a general idea of where a plane is and where it’s headed.

According to the Associated Press, Flight 370 may have been in contact with military radar in its final moments but whether a civilian air traffic controller knew where it was is less clear.

We know its transponder signal was lost just as it was supposed to enter Vietnamese air space and because transponders are meant to work with radar, that suggests the plane was close enough to shore to be on somebody’s screen.

Could somebody have turned off the aircraft’s transponder?

That’s a tricky question. Pilots can send coded messages over the transponder in an emergency. But we’re not really sure what happened to the transponder in this case.

We don’t know, for instance, if anybody tried to tamper with it.

But why would they?

Reports suggest that nobody on the plane made a distress call – no radio transmission, nothing.

That implies there wasn’t time to cry for help in the midst of a technical breakdown or a violent struggle. If that’s the case, it’s not likely an attacker – if there was one – would try messing with the transponder while they were still trying to gain control of the aircraft.

What about passengers’ cellphones? Could they be tracked?

The reason you can be tracked on land is because your phone is constantly talking to the cell towers that provide you service. No service? No location.

While you’re in the air, there’s not much of an opportunity to use your cellular network – although that’s changing in Europe and may soon begin to change in the US, too.

Technology now enables the use of cellular networks if a plane carries a special base station that sends communications to a commercial satellite, which then relays it to the ground.

But adoption will be voluntary among airlines.

Don’t phones often carry GPS chips?

Good thought. Yes, many cellphones do have GPS.

But it’s not the kind of GPS you’d find in a car.

Cellphones typically rely on a kind of “assisted” GPS – one that requires a constant data connection. Without wi-fi or a cell tower, you’re not able to connect with the satellite.

Did Flight 370 have wi-fi?

Wi-fi would almost certainly have helped.

Mobile devices such as tablets and cellphones on the plane would have been communicating with the internet right up until its other communications systems went down.

But Malaysia Airlines does not appear to offer in-flight wi-fi.

What other technologies might have helped maintain a fix?

The Federal Aviation Administration wants to move to a next-generation air traffic control system that uses GPS satellites to keep tabs on planes. It’s called, appropriately, Next Gen.

Satellites have a distinct advantage over radar – a technology that dates back to World War II – in that they can monitor wide swathes of territory, including oceans, but this system is years away.

Even if we had it now, the US’s national aviation authority is mainly concerned with domestic airspace.

Malaysia Airlines would not have been covered.

Speaking of satellites, US officials have examined spy satellite imagery from the region, and by the time of going to print had turned up no clues about what happened to the plane.