Tracking aircraft

The loss of MH17 was a true disaster.    It's a bit sobering to reflect that this is the very flight we travelled on last October (from Amsterdam to Kuala Lumpur).

However,  I was interested in the map that appeared on the internet shortly after the event, showing that hardly any commercial aircraft were near Ukraine.

On closer investigation, I find that you can see the location of a lot of the world's commercial  flights (including corporate planes) at Flightradar 24 and at Planefinder.   These sites use information transmitted from planes, particularly from ADS-B transponders (but also other sources).  They take a moment to load, but it's fascinating that this information is available to the world on just a click of the mouse button.  There are clearly some committed people out there that go to all this effort.

Just the same, some of the information looks a bit dodgy, particularly on Planefinder.  This site appears list a number of Aeromexico flights in Australia, but I think they are actually Pel-Air Aviation flights (do they use a similar flight prefix - perhaps something like AM)?   Also, Planefinder appears not to have a good coverage of China, but this doesn't seem to be an issue on Flightradar24.   Perhaps there are other strengths and weaknesses, too, but who's complaining, as the sites don't even carry advertisements.