Lockheed Skunk Works · 1964 to 1999

The SR-71 Blackbird in 100 facts

Thirty-two were built. None was shot down. A hundred things the legend leaves out.

OriginsSources
Plan view of the SR-71A Blackbird: long chined forebody, delta wing, two engine nacelles and canted twin tails.Lockheed SR-71A · 107 ft 5 in long · 55 ft 7 in span
Plan view of the SR-71A Blackbird, nose up.SR-71A · 107 ft long · 55 ft span
3.3Mach, at the top of the envelope
85,069 ftsustained altitude record, set 1976
2,193 mphspeed record, still standing
0lost to enemy action

01 · Where it came from

Before the Blackbird

The SR-71 was the last of a family the CIA started.

  1. Project Archangel. In late 1957 the CIA asked Lockheed for a spy plane radar could not catch. Kelly Johnson's Skunk Works drew 11 designs in 10 months.
  2. Ordered just before a shootdown. The CIA signed for a dozen A-12s in February 1960. Three months later Gary Powers's U-2 was shot down over the Soviet Union.
  3. The A-12 came first. The CIA's single-seat A-12 flew at Groom Lake (Area 51) in April 1962. It flew higher and faster than the SR-71 that followed it.
  4. A family of 50. 13 A-12s, 3 YF-12 interceptors, 2 M-21 drone carriers and 32 SR-71s were built.
  5. The interceptor that never was. The YF-12 carried a fire-control radar and AIM-47 missiles. McNamara withheld production money three years running, and the F-12B died in 1968.
  6. Mother and daughter. The M-21 carried a D-21 drone on its back: M for mother, D for daughter. After a fatal launch accident, B-52s carried the drones instead.
  7. Drones over China. D-21Bs flew at least four missions toward China's Lop Nor nuclear test site between 1969 and 1971. None brought its film home.
  8. Black Shield. A-12s flew the family's first combat missions over North Vietnam from Kadena, starting 31 May 1967.
  9. Announced as a cover story. In February 1964 President Johnson revealed the "A-11". It was really the YF-12, shown to hide the secret A-12.
  10. First flight. The SR-71 first flew on 22 December 1964 at Palmdale, California, with Lockheed test pilot Bob Gilliland.

02 · The airframe

Built to survive Mach 3

Mach 3 turns the skin into an oven. Most of the airframe is one long answer to that problem.

  1. 85% titanium. The rest is mostly polymer composite. Aluminium would have softened at skin temperatures near 600°F.
  2. Soviet metal. The CIA bought titanium through dummy firms, because Soviet output dwarfed America's.
  3. Distilled water only. Chlorine in tap water corroded welded titanium, so the parts were washed in distilled water.
  4. No cadmium tools. Cadmium-plated tools caused corrosion too. Contamination once rejected 80% of delivered titanium.
  5. Loose on purpose. Panels were fitted with gaps. Heat closed them, and the airframe grew several inches in flight.
  6. It leaked fuel. The same gaps let JP-7 drip on the ramp. That is not why it refuelled soon after takeoff: it took off light to spare its brakes and tires.
  7. Black is a heat decision. The paint radiates heat better than bare metal, which lowers skin temperature and thermal stress.
  8. Corrugated wings. Large sections of the inboard wing skin were corrugated, not smooth, to survive the expansion.
  9. Quartz window. The navigation window was solid quartz, ultrasonically fused to the frame. The windscreen outer pane hit 600°F.
  10. Precious tires. They contained aluminium and were inflated with nitrogen: $2,300 each, replaced about every 20 flights.
  11. Chines. The sharp edges along the nose were added to bounce radar away. They also made lift, which let designers drop the planned canard foreplanes.
  12. Tilted tails, sawtooth edges. The fins lean inward and parts of the skin were sawtooth radar-absorbing material, both to cut radar returns.
  13. About 10 square meters. That was its radar cross-section, from a wing of about 170 square meters. Johnson later admitted Soviet radar improved faster than the stealth did.
  14. Three-pane windscreen. The outer windscreen had three layers of glass with cooling sections between them.
  15. Air-conditioned nose wheel. The cockpit cooling system also cooled the nose gear bay, so only the main wheels needed the special aluminium tires.
Why the paint is black.

Not for stealth. Matte black emits heat faster than shiny metal, so the skin runs cooler.

03 · The engines

Two engines and a shock wave

At cruise the engines were almost passengers. The inlet did most of the work.

  1. Two J58s. 34,000 lbf each with afterburner, and they ran on continuous afterburner at cruise.
  2. The inlet does the work. Above Mach 3, the inlet made 54% of the thrust, the nozzle 28%, the engine 17.6%.
  3. Turbojet, then ramjet. It took off as an afterburning turbojet and behaved like a ramjet at cruise.
  4. 800°F intake. Compressor inlet air reached 800°F, and the turbine ran continuously at 2,000°F.
  5. Six bleed tubes. They moved 20% of compressor air to the afterburner, the fix that made Mach 3 practical.
  6. Unstart. If the inlet shock jumped forward, the jet yawed violently and helmets struck the canopy.
  7. Digital fix. A digital inlet control arrived in 1980 and sharply cut unstarts.
  8. Green flash. JP-7 was hard to ignite, so a shot of triethylborane lit each engine with a green flame.
  9. Fuel as coolant. JP-7 cooled the airframe and electronics before it was burned.
  10. 90-minute legs. A supersonic run lasted about 90 minutes before it needed a specialised KC-135Q tanker.
  11. Started by two Buick V8s. The AG330 start cart used two Buick V8 engines on one shaft to spin each J58. Compressed-air starters replaced it later.
  12. No electric starter. The fuel-based cooling system could not handle one, hence the start cart and the chemical ignition.
  13. 20 seconds to lift-off. It rolled 4,500 ft and reached 240 mph, climbed to 20,000 ft in under two minutes, then needed 17 more minutes and a third of its fuel to reach 80,000 ft.
  14. Faster was cheaper. Mach 3.15 burned about 36,000 lb of fuel an hour against 38,000 at Mach 3.0. Cold air cut it further.
  15. The speed limit was heat. Mach 3.2 was the limit, raised to 3.3 only if air entering the compressor stayed under 801°F.
  16. 3,200°F afterburner. Ceramic coatings and cool compressor air let the afterburner run at full power for hours.
  17. Its own tanker. KC-135Qs had a high-speed boom and kept the jet's JP-7 apart from their own fuel. Any other tanker meant a Mach 1.5 limit afterwards.
  18. Afterburner on the boom. On hot days, as it neared its 80,285 lb fuel load, the pilot ran the left engine in minimum afterburner just to keep up with the tanker.

04 · The crew

Two crew, one pass

Nobody rode in this aircraft. They wore it.

  1. Two seats. Pilot in front, reconnaissance systems officer behind.
  2. Pressure suits. Above 43,000 ft a mask cannot supply enough oxygen, so crews wore full pressure suits.
  3. Ejection heat. A Mach 3.2 ejection exposed the crew to about 450°F.
  4. Fast landings. Touchdown came above 170 knots, and a drag parachute saved brakes and tires.
  5. One a week. Each jet averaged one flight a week; 19 hours of preparation if everything was ready.
  6. One fatality. Twelve SR-71s were lost in accidents, and one SR-71 crew member died: Lockheed's Jim Zwayer, in 1966. The CIA's A-12 program lost two pilots.
  7. First woman. NASA engineer Marta Bohn-Meyer became the first female SR-71 crew member in October 1991.
  8. Lunch through a port. Food came in toothpaste-style tubes fed through an opening in the helmet. Crews steered drinking straws in with a mirror.
  9. A hot cockpit. The inside of the windshield reached 250°F. Cockpit heat was dumped into the fuel before it was burned.
  10. A line across the panel. A peripheral vision display projected a faint horizon line across the whole instrument panel to help the pilot during refuelling.
  11. Stars in daylight. The astro-inertial navigator tracked stars day and night from a catalogue of up to 61, holding the track to within about 1,000 ft at Mach 3.
  12. Mexico by accident. The first international SR-71 sortie, in July 1967, happened when the navigator failed on a training flight and the crew strayed into Mexican airspace.
  13. Thrown clear at Mach 3. When 61-7952 broke up in January 1966, pilot Bill Weaver survived. His crewmate Jim Zwayer did not.
  14. Cut ties. In 1968 a chief master sergeant began the Habu tradition of cutting off neckties.

05 · The mission

The mission was the point

It carried cameras and antennas, never a weapon. The photographs were the product.

  1. 3,500 lb of sensors. Cameras, side-looking radar and electronic intelligence gear.
  2. Big lens. The KA-102A camera had a 36–48 inch lens.
  3. Overt, not covert. USAF markings, and pilots carried Geneva Convention identity cards.
  4. Borders, not overflights. It never overflew the Warsaw Pact or China; routes hugged coastlines.
  5. 800 missiles. North Vietnam fired about 800 SAMs at SR-71s; none hit. One passed within 150 yards.
  6. Swedish lock-ons. Viggens claimed missile lock on 51 of 322 Baltic Express sorties between 1977 and 1988.
  7. MiG-25 shadow. A Foxbat could close to 3 km behind at 62,000 ft, then had to break away.
  8. 1987 escort. An engine exploded over the Baltic, and two Swedish Viggens escorted the damaged jet out.
  9. D.B. Cooper. In 1971 an SR-71 flew five sorties trying to photograph the hijacker's escape route. Cloud spoiled every one.
  10. Far from Russia, too. Missions also went over Cuba, Nicaragua and Libya, and probed nuclear sites in Israel and South Africa.
  11. The busiest Blackbird. 61-7976 flew the first operational sortie on 21 March 1968 and logged 942 sorties, more than any other. It is at the USAF museum in Dayton.
  12. From weekly to daily. Vietnam sorties ran about once a week in 1968 and nearly every day by 1972.
  13. Slowing for Sweden. On the Baltic route it slowed to Mach 2.54 to turn south of Åland. At Mach 3 the turn would have crossed into Swedish airspace.
  14. Ordered shot down. NSA data later showed MiG-25s scrambled to shoot down the crippled 1987 jet, and one locked a missile on it. In 2018 the four Swedish pilots received US Air Medals.
  15. Horizon to horizon. An Itek Optical Bar Camera photographed continuously from one horizon to the other.
  16. Mach 3.5, reportedly. Pilot Brian Shul wrote that he passed Mach 3.5 over Libya on 15 April 1986 while evading a missile.

06 · The records

Records that still stand

The last records were set on the way to a museum.

  1. 2,193.2 mph. Set on 28 July 1976 over a straight course. Still the record for a manned air-breathing aircraft.
  2. 85,069 ft. Sustained horizontal flight, the same day. Still the altitude record.
  3. 1h 54m 56s. New York to London on 1 September 1974, averaging 1,807 mph.
  4. 64m 20s. Los Angeles to Washington on 6 March 1990, averaging 2,145 mph.
  5. Four in one flight. The same delivery flight set West Coast to East Coast at 67m 54s.
  6. Fleet totals. 3,551 mission sorties, 53,490 flight hours, 11,675 of them at Mach 3.
  7. Still standing. Fifty years on, no aircraft has beaten either 1976 record.
  8. 15,000 miles nonstop. In April 1971 one jet flew more than 15,000 miles in 10 hours 30 minutes and won the Mackay Trophy.
  9. Beat Concorde by an hour. Concorde's best New York to London was 2 hours 52 minutes. The SR-71 did it in 1 hour 54 minutes.
  10. St. Louis to Cincinnati in 8 minutes 32 seconds. Another record from the 1990 delivery flight, at 2,190 mph.
  11. 2,242 mph. The Air Force clocked the 1990 delivery flight at this speed at one point.
  12. Faster than a bullet. At 2,193 mph it covered a mile every 1.6 seconds, faster than a typical rifle bullet leaves the muzzle.

07 · The odd corners

Odd corners and the afterlife

  1. The RS-71 that never was. The press transcript said RS-71 while the president said SR-71, which started the story that he misread it.
  2. Habu. Okinawans thought the jet looked like a local pit viper, and the crews kept the name.
  3. Senior Crown. The program's code name. Kadena deployments were Glowing Heat.
  4. A wing in Norway. One Blackbird landed there and left with a replacement wing and engine.
  5. Twice retired. The USAF retired it in 1989, reactivated three in 1995, and retired it for good in 1998.
  6. NASA's last. NASA flew the final Blackbird on 9 October 1999.
  7. Never matched. It carried no guns, bombs or missiles. Speed and height were the whole defence.
  8. $85,000 an hour. Dick Cheney gave the Senate that figure. Opponents put support at $400 to $700 million a year; it was closer to $300 million.
  9. Missed in the Gulf War. Months after retirement, General Schwarzkopf was told the fast reconnaissance an SR-71 could have flown was not available for Desert Storm.
  10. Back under budget. Skunk Works returned three jets to service in 1995 for $72 million. In 1997 President Clinton tried to cancel the money with a line-item veto, which the Supreme Court later struck down.
  11. Buried in the Mariana Trench. The last Blackbird lost, 61-7974, crashed off Kadena in April 1989. Its wreckage was buried at sea in the Mariana Trench.
  12. "The Bastard." The one SR-71C was built from a wrecked YF-12A's rear and a test-article front. Its odd yaw turned out to be a misaligned pitot tube.
  13. The only one abroad. 61-7962, which set the altitude record, is the only Blackbird displayed outside the US, at Duxford in England.
  14. A successor on paper. Lockheed's Mach 6 SR-72 was announced in 2013. It is still a concept.
  15. Maybe flying again. In September 2026 news outlets reported that NASA had contacted former engineers about returning NASA 844 to flight.