I saw what looked like an Extra & Cessna flying in formation a few days ago.....
But also, on the same day i saw two WWII fighters (couldn't tell what type they were)
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All went up the Thames Estuary you say, they may be practicing for the Southend Airshow perhaps but surely not already?
Unless, they are practicing now so that if any faults/tech problems occur the a/c can be repaired in time
Again, i don't know if my sightings are connected with what's going on!