Sitting in (a sunny, for a change) Solihull, something fairly load and not-airliner type noise just passed nearby. ADSB gives no clues other than a
Learjet 45 which passed overhead at ~10000ft having done a ~220 degree right turn after takeoff from BHX R33. What piqued my interest was the noise it sounded more like a fighter jet, and hung around for a long time (i could still hear it whilst said Learjet was over Wellsbourne, 20-odd miles away) - in contrast to watching airliners take off when the noise returns to background within a minute or so of passing overhead.
Toggling the military filter on reveals nothing anywhere near.
Any clues?