It is quite possible that a Mach 6 stealthy reconnaissance aircraft called the Aurora
has been developed to replace the Mach 3 SR-71 Blackbird.
The top secret Aurora project has probably been underway since 1987 with a first flight in 1989 and
becoming operational in about 1995.
There have been reports of hypersonic aircraft travelling at speeds from Mach 3 to Mach 6 over Scotland
by the remote RAF base at Machrihanish, Strathclyde.
It is believed that the Aurora was being flown from a base in the Nevada desert to an atoll in the pacific then
on to Scotland to refuel before returning to the US at night via the north pole at Mach 6. Before the Aurora lands
an F-111 is scrambled to fly in close formation to confuse prying eyes.
The Aurora could be using liquid methane for fuel and specially adapted tankers could refuel it in the air. It is
most likely made of Titanium with the outer edges made of Inconel (heat resistant stainless steel). At a cruising
speed of Mach 5 the leading edges would glow red and reach a temperature of 1000 degrees Fahrenheit.