Good call, but alas, very boring.
Hopefully this is all a coverup and it was an extraterrestrial spacecraft.
"... 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. Specially modified tanker aircraft are being used to top up Aurora's tanks with liquid methane fuel in mid-air... The US Air Force is using the remote RAF airbase at Machrihanish, Strathclyde, as a staging point... The mystery aircraft has been dropping in at night before streaking back to America across the North Pole at more than six times the speed of sound... An F-111 fighter bomber is scrambling as the black-painted aircraft lands, flying in close formation to confuse prying civilian radars."
"The sleek aircraft would cruise at Mach 5 (3,350 mph) speed at a maximum altitude of about 100,000 feet. The aircraft would be made primarily of titanium with its outer edges constructed of Inconel, a heat-resistant stainless steel. At Mach 5 speed the leading edges of the air-frame would glow red above 1,000 degrees Fahrenheit. "