Here in the UK it is quite a rare event, most recently at RAF Leuchars airshow we were to be treated to a few 'old and new' flyby's but the weather interveined and ruined the chance of it happening. The most recent occurance i can think of is when the Army Air Corps had the Blue Eagles team and their Historic flight flew in formation at Biggin Hill airshow. Also with the RN Sea Harrier being retired it has appeared with the RNHF a couple of times. But overall it is really quite rare.