I had the same impression as well : http://www.flightradar24.com/

xadoc · on March 8, 2014

there is a 250-400 km range for FlightRadar, it does not cover oceans very well.

http://www.flightradar24.com/how-it-works "Flightradar24 has a network of more than 3,000 ADS-B receivers around the world that receives plane and flight information from aircraft with ADS-B transponders and sends this information to our servers. Due to the high frequency used (1090 MHz) the coverage from each receiver is limited to about 250-400 km (150-250 miles) in all directions depending on location. The farther away from the receiver an aircraft is flying, the higher it must fly to be covered by the receiver. The distance limit makes it very hard to get ADS-B coverage over oceans."

jebus989 · on March 8, 2014

Looks like they did a pretty good job:

https://twitter.com/flightradar24/status/442145510615289856

After hours of misinformation re: "2 hours into flight", the airline apparently agreed with the flightradar data:

https://twitter.com/flightradar24/status/442222070727204864

JonnieCache · on March 8, 2014

I was thinking more about NORAD and the like.