Top 10: The fastest aircraft ever made

8: General Dynamics F-111 Aardvark – Mach 2.91+

The F-111 bomber was the result of a failed project to build a fighter-bomber capable of serving both the United States Air Force and Navy as both a fighter-interceptor and a fast bomber. The naval fighter version for aircraft carriers, the F-111B, proved too heavy and sluggish to serve and was cancelled in favour of the F-14 Tomcat. Open any aircraft reference book or website and you’ll read that the F-111 had a top speed somewhere between Mach 2.2 and Mach 2.5. But when the Hush-Kit site spoke to F-111 pilots and navigators he found that this official number is rather modest.  Aardvark Weapon System Officer Jim Rotramel noted, “There was NO specified maximum speed.”

8: General Dynamics F-111 Aardvark – Mach 2.91+

“What we had was a heat sensor on the windscreen. When the sensor got hot enough, it caused a caution light to illuminate…warning was that if the timer reached five minutes, the windscreen would melt. I think the fastest anyone ever claimed to have gotten was Mach 2.91. In any event, no one ever saw the jet stop accelerating—everyone decided to back off before testing the egg timer…” Following this interview, other former F-111 aircrew came forward claiming even greater speeds achieved, some as high as Mach 3.2 (we’ll stick to Jim’s already high claim). The F-111 was capable of such speeds due to the extreme sweepback angle possible with its variable ‘swing-wings’, its jet air intake design, general slimness and the type of engine.

7: North American XB-70 Valkyrie (1964) – Mach 3

Until the late 1950s everyone knew that each successive generation of bombers was faster and higher flying than the last. They had to be, as the fighters tasked with blowing them out of the sky were getting ever faster and higher flying. The next step was Mach 3, three times the speed of sound – or around 2000 mph, at 75,000ft. The resultant aircraft was arguably the most impressive machine that ever flew: a sleek 56-metre-long white dart with a delta wing with outer sections that folded down by 65 degrees during high-speed flight. Despite its beauty, the B-70 fleet was designed to annihilate hundreds of thousands of civilians or highly protected nuclear missile silos with free-fall nuclear bombs.

7: North American XB-70 Valkyrie (1964) – Mach 3

It was hoped that the bomber’s performance would render it invulnerable to manned interception, but it was soon clear that ever more potent surface-to-air missiles were a real threat. Intercontinental ballistic missiles were the future, but the XB-70 project had momentum. It became a political ‘football’ kicked around by the most powerful men in America, including Richard Nixon, John F Kennedy and Robert McNamara, all adopting pro or anti positions as suited their needs. Kennedy was pro-B-70 in the 1960 election campaign but changed his mind. The aircraft was cancelled, but did perform some research work for NASA.

6: Bell X-2 Starbuster - Mach 3.196 (air-launched)

In 1947, the Bell X-1 broke the sound barrier, and a mere eight years later the X-2 was going three times faster, and was the very first aircraft to go faster than Mach 3. It was rocket-powered, with a swept-wing. It was launched from beneath a Boeing B-50 mothership. The project started as early as 1945, with the Bell Aircraft Corporation, the United States Army Air Force and the National Advisory Committee for Aeronautics (NACA) teaming up to study the aerodynamic issues of extremely fast and high flying.

6: Bell X-2 Starbuster - Mach 3.196 (air-launched)

To withstand the high skin temperatures the X-2 used stainless steel and K-monel (a copper-nickel alloy) in its construction. The X-2s were powered by a two-chamber Curtiss-Wright XLR25 throttleable liquid-fueled rocket engine. Once the rocket had used its fuel out the X-2 made an unpowered glide back to land. Capt. Milburn G. “Mel” Apt became the first person fly faster than three times the speed of sound on Sept. 27 1956. He reached 2094 mph (Mach 3.196) in the Bell X-2, but tragedy soon followed. Apt performed a sharp turn, causing the aircraft to tumble uncontrollably. Though Apt escaped from the aircraft, he was killed as he hit the ground in the escape capsule.

5: Mikoyan MiG-25 ‘Foxbat’ - Mach 3.2

The Mikoyan MiG-25 was a 1960s Soviet aircraft conceived with several roles in mind. It needed to be fast enough to catch the US A-5 and (later cancelled) XB-70 bombers, as well as perform the reconnaissance and recce-nuclear-bomber role. For these roles, it was intended to rely on high speed and high altitudes to succeed. Whereas the US SR-71 Blackbird relied on exotic technology, fuel, engines and materials to reach high speeds, the Soviet Union used a largely stainless steel construction to withstand the huge aircraft skin temperatures and very large engines. This simple solution was far cheaper but meant it was slower and couldn’t achieve tri-sonic speed for very long.

5: Mikoyan MiG-25 ‘Foxbat’ - Mach 3.2

For most of its life, it was used in the interceptor and reconnaissance roles, and it was in the latter role that it was caught on Israeli radar flying at Mach 3.2. This was well above the recommended normal limits of Mach 2.83 and is said to have wrecked the engines. In 1976 Soviet Air Force fighter pilot, Viktor Belenko, defected to Japan in a MiG-25. Before the aircraft was returned it was hurriedly assessed in detail by Western intelligence agencies. The MiG-25 had been much feared, but studying the aircraft revealed it had far lower tech than expected.

4: Lockheed SR-71 Blackbird - Mach 3.3 (1964)

Produced in huge secrecy, the Lockheed SR-71 Blackbird was a technological marvel that seemingly arrived from space. The sleek alien looks of the SR-71 were utterly appropriate for a machine many years ahead of its time. The Blackbird was penned by the great aircraft designer Kelly Johnson, in Lockheed’s legendary Skunk Works advanced projects department. The SR-71 could travel over 33 miles every minute. Key to the Blackbird’s high speed were its unusual engines and their relationship with their inlet shock, its special fuel, the aircraft’s low drag shape and sharp wing sweep, its use of titanium, and its cooling systems.

4: Lockheed SR-71 Blackbird - Mach 3.3 (1964)

Mach 3.3 is the traditional quoted top speed of the SR-71 but more recent articles have put it at Mach 3.5 (and in some cases Mach 3.75). We’ll stick to the quote given directly to us by a SR-71 pilot, which is that it was fully tested up to Mach 3.3 (though it is said to have been ground-tested to Mach 3.6) The Lockheed SR-71 Blackbird supplied the US with vital intelligence for much of the Cold War, proving invulnerable to interception. It is the fastest crewed aircraft – and fastest jet – to ever see military service and retains a cult bewitched by the mystique of this charismatic futuristic aeroplane.

3: Lockheed YF-12 - Mach 3.35 (1963)

The swiftest fighter aircraft ever created, the Lockheed YF-12 was a prototype for an advanced United States Air Force interceptor able to fly incredibly fast, with a belly full of ultra-long range AIM-47 air-to-air missiles to knock out Soviet bomber threatening the United States. Though this sounds formidable, there were several flaws with the concept, one being that the YF-12 with its many exotic features, could not be quickly scrambled. It took much too long to prepare the aircraft for flight, a bad quality in an aircraft intended to intercept enemy bombers at a moment’s notice.

3: Lockheed YF-12 - Mach 3.35 (1963)

Another issue was its use of special JP-7 fuel. This meant it could not be air refuelled by normal tanking aircraft and would have to rely on a special fleet of tankers of Boeing KC-135Qs. The SR-71 would require 56 KC-135Qs, a hugely expensive effort – a force of F-12s would have required far more. It was clear that a slower more conventional aircraft with long-range missiles would be a far easier and more effective option and the exciting F-12 was cancelled. Though cancelled, much of the long-range missile and radar technology developed for the A-12 would go on to inform the later Grumman F-14 Tomcat.

3: Lockheed YF-12 - Mach 3.35 (1963)

‘Project Oxcart’ was a highly classified project to develop a reconnaissance aircraft for the US, that thanks to high speed and altitude performance would be immune to enemy interception by either fighters or surface-to-air missiles. It would also pioneer the yet-to-be-named concept of radar stealth. The two entries above are essentially the same aircraft, but the single-seat A-12 was the first family member. The A-12 was beyond state-of-the-art, with many technologies required to be invented to make it possible.

2: Lockheed A-12 ‘Cygnus’

At 30 metres, the A-12 was very long for a single-seat aircraft. It was designed for prolonged flight at Mach 3, so required titanium in its construction to survive a skin temperature reaching between 300 and 400 degrees. Such high-speed flight was enough to lengthen the aircraft, and it would only contract again was cool. Though its maximum speed is often stated as Mach 3.35, it is likely that the A-12 was capable of even faster speeds with Mach 3.6 very possible. It flew operational missions for a short time before being replaced by the twin-seat and considerably more capable SR-71 Blackbird.

1: North American X-15 - Mach 6.7+ (1959)

The record for the fastest speed for a crewed aircraft has stood for an astonishing 57 years. The North American X-15 was a research aircraft built to explore extremes of speed and altitude. The X-15 reached an astonishing 4,519mph Heat resistance came from the use of heat-resistant nickel alloy (Inconel-X 750). Earlier flights used the XLR11 rocket engine which used ethyl alcohol and liquid oxygen. The majority of flights (175 of 199) used the XLR99 which employed anhydrous ammonia and liquid oxygen as propellant.