As you imply there was a vapor trail so it can't be the ISS, but by coincidence, the ISS was exactly 20 km due south of Wilson's Prom 8 mins later at 15:40:53
Just at that point, it was 439.37 km up and dawdling along at 27509.63 km/h
and dialled up the appropriate date and time but could not see anything there that fits your description.I'm not saying it wasn't there,just that it doesn't seem to have been recorded.
Not taking the piss here, but a meteor in daylight may may look similar to that.
Otherwise there have been plenty of military aircraft that have used our airspace, I believe the U2's used to fly around OZ and rumor has it they used have to get clearance to descend back in to class A
Guys, sure there are UAVs and other secret squirrel stuff in our airspace, but you would be surprised how high an F/A-18 can fly. Also, vapour trails only occur at a certain altitude/temp range, and disappear as you go higher. Being relatively small, a Hornet at around 25,000 feet will probably look, from the ground, like a high altitude aircraft leaving a thin trail.
and dialled up the appropriate date and time but could not see anything there that fits your description.I'm not saying it wasn't there,just that it doesn't seem to have been recorded.
Well done rjtjrt - that Plane Finder site is a good get, but it doesn't show the object of my interest.
Given the likely speed involved it must have been something military and perhaps relatively stealthy. I'm obviously wrong about the time - maybe it was 30 or 40 seconds to traverse 90 degrees.
