They are never known. Commercial flights are not painted, they report their IFF, and on oceanic flights there is no one providing positive control. Essentially, you check in when you get there and flight times/routes are sequenced. But that sequence changes minutely as flights are delayed or have to alter course for weather.
You would have to have someone positively identfying every outbound track of everyone of the thousands of commercial airliners leaving daily. Then you would have to also have to delouse every single one of them to ensure that a Badger bomber didn’t slip up into trail on them.
Reality is not even close.