Thank god. I was hoping for such an expert insight since the start. I don't know the industry practices let alone for Air Force. I've forgotten about you, otherwise I'd had you mentioned since my first post.
I would think a foreign
military plane fly over the airspace of an
allied country, over the landmass of the country itself would be required to have FR24 turned on.
Can you have a look on that YouTube video (last Twitter thread) and give us your comments?
I don't really want to meddle into the NordStream saga as I believe we won't have the facts necessary to know who did what until at least the war in Ukraine is over and possibly the current Russian administration gone. There are enough ideas floating around that, with the right dose of confirmation bias, could lead to any conclusion.
But I took a brief look at that Twitter thread and bits and pieces of the Youtube vid. And I can assure you that the guy behind that video is making a big deal out of stuff that could mean everything or absolutely nothing. But when he makes the "NO CALL SIGN" thing sound important, it proves he is clueless when it comes to what the information means.
Flightradar24 is just a civilian website by aviation nerds, for aviation nerds. Everything it presents on the website is dependent on information that is either available from the data transmitted by aircraft, or data entered by users (for example, it is not given that FR24 knows the aircraft registration and type, even if the transponder mode transmits a unique ID for that aircraft. That depends on someone knowing the aircraft entering that info).
To give an example, I frequently see aircraft from our club showing up with "NO CALLSIGN" and then later being shown with the registration as their callsign, and I know that there is nothing we can do from the cockpit to influence that. We set our transponder into "altitude" mode before takeoff and keep it there until we land.
The transponder is basically a receiver/transmitter unit that registers a signal from ATC radar, and sends a signal back to say "here I am". This signal can contain more information, and this information can be used by anyone who can receive it. FR24 and similar websites use ground-based receivers to pick up that information, much like ATC would.
Now, military aircraft usually have transponders with all the "civilian" modes available, and then some more (usually so they can show their position and identity to friendly aircraft without revealing the same information to enemy aircraft). When they fly with their transponder set in what we call "mode S", the standard setting for civilian aircraft with modern transponders, all other aircraft can see their identity, altitude, heading. This is actively used by traffic coillision avoidance system (TCAS) which all airliners have.
Now, military aircraft don't always use Mode S, but even when they don't, they usually have their transponder switched on. But FR24 might not be able to parse the information and show it. ATC still could. In some cases, but this is rare in peacetime, military aircraft could be allowed to fly in controlled airspace without ATC following, but that would mean they had full responsibility for separation from other aircraft and that would be dangerous. So that' very unlikely, except in areas that have been designated as danger areas. This would be publicly available information for all pilots, airlines etc.
But all this is completely unrelated to the callsign shown on FR24. Just that you can't see the callsign on FR24 doesn't tell you anything except the pilots might not have entered the callsign for that particular flight into a data system that FR24 has access to.
Also, the information could be available but FR24 would be asked not to show it. This is why for example most fighter jet flights don't show up even when they fly in civilian airspace with transponder in civilian mode.
Bottom line, "no callsign" is not mysterious, doesn't tell anything about the nature of the flight, and by the way - which information would the flight callsign give you that you didn't already see in the video? Aircraft type? Shown. Full route? Shown.
Feel free to continue this discussion, but accept it will be without me.
