Aircraft seen variation


Appreciate this is not an exact science but curious as a fair discrepancy here.

I have a Pi running PiAware, I also feed FR24 and ADSBx.

Earlier today I checked some statistics and noticed that Flightaware showed 717 aircraft spotted whereas FlightRadar24 showed 673 - a difference of 44 aircraft which is around a 6% difference.

Both are enabled for mlat - I do appreciate times data is processed may be a factor too.

As many FA enthusiasts also share data to other ADS-B trackers curious as to other views on data comparison.


The reporting times (actual hours of the day) are different (FR24 is UTC). Because of the hourly variation of planes “density”, that makes a difference.
For me is FA= 2090, FR24= 2078

I don’t feed ASBx because they are a foreign information gathering op. I will not participate willingly in that.

Good point about UTC difference.

Not heard any criticism of ADSBx before - didn’t think there was any financial gain, which I assume there must be for FA and FR24


I am not talking about direct financial gain. Is adding intelligence gathering, and that is sometimes priceless.

Imagine in WWII that Germans would have some “hobbyists” reporting the movements of the English airplanes in UK air space. No direct financial gain from the “hobbyists”. Would they still be spying for the enemy? Sure they will.

China, Russia, and anyone else having direct, free, access to all the movements of the national air forces (think MLAT), because they can “see” them now (don’t know what country are you from, but I guess it doesn’t matter). If you think that that will bring “world peace”… fine, your choice to be fulled by that. But deterrence info-swapping is already done via official channels of reporting.
I personally think is aiding and abetting foreign nations intel gathering efforts.

LE: That applies for private corporations too. Imagine that you can track freely the movements of the private jet of the CEO of competitor company. Wouldn’t that be nice to know?

I suppose you could be right but the Russians used to give US astronauts a lift to the ISS, I’m sure some data got shared there. Orbiting satellites have better cameras than professional photographers so if certain data was secret I’m sure Governments would make something illegal or encrypt positional data. The technology is there.

I am based in UK.


While I don’t disagree, I would think a FIS has other means to track this traffic. Worst case scenario, a receiving station of their own, and no web tracking.

Also, what you see is likely not important in military terms. They must have other ways to mask it in real situations, if only to switch off their ADS-B transponders.

I have no interest in military traffic, blocking it is fine with me.

Monitoring of any kind has potential ‘dual’ use.

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True, but irrelevant for on-going air traffic monitoring.

With ADS-B moving to satellites, this is where worldwide monitoring will be done, unless it’s encrypted.


absolutely not. nothing ‘they’ don’t already know.
if it did, sdr dongles, FA, FR24 et al, would have been illegal !


Remember when GPS had ‘selective availability’? It was removed in 2000, and gave ‘birth’ to Geocaching, among many other applications and uses.

Radio scanners before that. In the case of scanners, it was decided in most jurisdictions to digitize and encrypt the traffic.

Bottom line: if there is a considerable security risk, it will not be ‘freely’ available, for long.


There is a legal reason why FA and FR24 need to “hide” some airplanes. Both military and commercial. And also they “change” slightly the locations of others (both space and time delay).

You guys can thing what you want, I exposed my thoughts above. I don’t want to waste my time explaining why your stated “reasons” are valid, because I know they are not. You can help feeding the ADSB Exchange… with MLAT data (above I have said clearly this is not about ADS-B).

PS: The Russians and Chinese don’t want that some of their planes be tracked in real time either. So… that’s that.

You raise a decent point about mlat data - I have temporarily disabled mlat to ADSBx until I enquire more about the security implications.

There will always be disagreements around security as well as paranoia with that possibly the most dangerous problem we have in the World.


As far as the military goes, it’s called OpsSec. I doubt your receiver is a security hole to their operations. If that is so, we are in serious trouble. May they invoke the Patriot Act, or whatever, immediately, and put an end to this vulnerability.

I would be surprised if the military relied on FA, FR24, etc. The companies in turn would have no interest in providing this kind of info to the general public, i.e. potential clients. Hobbyists are not their ‘market’.

The delay is in place to protect commercial flights, not military. The blocks are mostly requests from private/corporate plane owners.

As for MLAT, a position less transmission is still required. Rest assured their modeS transponders are off during missions. Airshows don’t qualify as missions to me.

Apologies for the off-topic. Last one from me.

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ModeS is not turned off during during training, to protect civil air traffic, especially when the base is very close to a commercial international airport.
Aggregating data can give more info than you think.
Like, a simplified example, increased training patterns of flight, coupled with… some other collateral data indicators (heck even real-time auto traffic can be seen) can divulge that a deployment of a carrier is imminent and other associated info.

Like I said, I don’t feel the need to help intelligence gathering (military or commercial), even if there others that will happily do that. Personally I am content with the way FA and FR24 are dealing with the privacy protection.

Yes, I tend to agree with you, there is much paranoia and conspiracy theorists abound.

However, that said I started out with FA and have been perfectly happy with their system, started feeding FR24 as their live web page has a facility which FA doesn’t have. ADSBx seemed to have a decent intend, hence feeding them.


MLAT, dump1090/978, and such software are already open-source and freely available everywhere. There’s nothing stopping a bad actor or nation state from deploying multiple cheap receivers around “interesting” areas and shipping the Mode-S data back home to an MLAT server. As all of us here are aware of, the barrier to entry for aircraft spotting/mapping is only $50 in hardware plus an internet connection.

I want to believe that, those who look at this kind of threat as their profession, have already assumed and planned that potential bad guys already have ADS-B/MLAT, etc capability, and have adapted accordingly with going RF dark, satellite comms, or with encrypted location data.

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Really? How many ADSB stations (with MLAT) you think did “they” deploy from their own money, using their own operatives?

And how many are getting for free?

PS: This works for every nation, I don’t say that there “good guys” or “bad guys” because it all depends of perspective. China has a big firewall around everyone in their country, they don’t think that “enemy already has that”.