Flightradar24's data comes from a network of volunteer-run ADS-B receivers, which explains why the coverage is so much better over the US and Europe where there are lots of volunteers with their own ADS-B receivers than the rest of the world where there are not. Note for instance how coverage in Africa really only picks up again in South Africa around the major cities.

ADS-B transponders are also not yet required on all aircraft outside of Europe so many planes don't have them and won't show up on this site.

Some airline pilots will only activate certain modes of their ADS-B transponders in flight after take-off, particular those used to broadcast velocity and position, so it's possible that's what happened in your case.

For all other cases the upload from the ADS-B receiver to the Flightradar24 site will be as real-time as is possible with standard internet infrastructure.

Learned something new today. Till this moment I didn't know about ADS-B. Quick link or people like me - http://en.wikipedia.org/wiki/Automatic_dependent_surveillanc...

Lots of stuff is happening in other domains too..

So the data is collected by volunteers... Sadly, there seems to be no indication of the license, no API (yet), and no way to download dumps...

As a data point they are dead on for Melbourne, Australia. Judging by watching the map and hearing the plane go over.

Same in Brussels, Belgium. Amazing to see and hear the real plane and at the same time watch in on a map.

Actually, that's pretty good! Can you estimate the lag time (for you)?

In the US at least, the FAA's official data feed (ASDI) is delayed by at least 5 minutes. The undelayed data is only given out on an as-needed basis (e.g. to airline operators) and can't be redistributed to the general public.

I stumbled into the about section, and in there they mention they're using a fleet of 500 volunteer ADS-B receivers networked to a central server, and they actually just pick up on planes with ADS-B transponders (more common in Europe than the US, it seems) - http://www.flightradar24.com/about - so it looks like they're not aggregating official/moderated data feeds or anything.

FlightRadar24 nevertheless follows the FAA 5-minute rule. In other countries, there is even a delay of 10 or 15 minutes.

In Switzerland, the federal aviation authorities tried to impose a delay as well. After a wave of protest pointing out the absurdity of such security through obscurity – you can see aircraft in the sky after all! -, a delay is no longer necessary and you can check in real time which aircraft is flying over your head at the moment (if equipped with ADS-B).

I'm not sure it follows the 5-minute rule for non-FAA data. I've watched, for example, an Emirates A380 go over my flat (near Heathrow) almost exactly as it's passing on the FlightRadar24 map.

They recently added FAA data to the US map (go to Settings on the left and tick "Show FAA traffic").

Near London, UK here. Almost exactly realtime for me.

Mind-blowing accuracy actually. Sky is clear out so I just looked out my window, saw two planes going in opposite directions.

Looked at the site, and there they were. Really cool!

You could hack a tablet app to find out which way the tablet is oriented, and using the flight data, annotate the image from the camera with the phone information.

Also, to nit pick again. The data from India seems to be wrong. There seem to be only 3-4 commercial passenger jets in the sky. This is impossible because most major Indian hubs are always backed up on the landings and departures.

Again to nit-pick: it's not wrong, it's just not exhaustive :)