You never know what will show up on display days. I believe they've had a visit from a Harrier in the past although I never saw it. A RAF Jaguar blasted through last season & they don't come much faster or noisier than that.
I've seen various things appear over the years, and it seems that the amount of RAF/RN heavy (jet) metal has decreased. I think that Shuttleworth has "lost out" to the greater number of "smaller" shows and venues that have appeared over the past decade, and who rely heavily on the MoD's assets. Thankfully, Old Warden has enough home owned aircraft to make every display different, and enough spare cash/pilots who have other connections as Doug said (eg RNHF, some of the smaller Duxford operators, BAE SYSTEMS etc).
) to Bruntingthorpe on an open day, have your ears blasted out by a Lightning fast taxi run! Not only are you deafened by the noise of the Avons in full afterburner, you get the sea of car alarms afterwards!
