probably a US stealth thingy going into its secret scottish base.............
You could be right, Rescue3 - except that, unless there really is an 'Aurora' (who knows?), nothing goes that fast these days, apart from short range fighters. As far as I can make out, the fastest bomber is the B-1B, max M1.3-ish (excluding the Russians and Chinese, of course). And, also as far as I can make out, the SR-71 Blackbird (M3+) hasn't flown since 1999, and the suggested SR-72 (hypersonic) doesn't (yet?) exist.
All total speculation, of course. Don't expect this post to last long.... (like UFO sightings?)
airsound