Lockheed L-2000: The American SST That Lost to the Boeing 2707

by Connor Kerr | Sep 18, 2026 | Mundo de la aviación, Historia y leyendas | 0 comments

On 31 December 1966 the Federal Aviation Administration chose which American company would build the aeroplane that was going to make Concorde obsolete.

Lockheed lost. The reasons given were, in effect, that its aircraft was too sensible.

The L-2000 was judged simpler to produce and less risky than Boeing’s design. It was also slightly slower off the runway, slightly slower at the top end, and likely to be louder. Boeing won because its proposal was more ambitious. Four and a half years later Congress killed the Boeing aircraft before a single one was built, and Boeing had by then quietly redesigned it to look rather like the Lockheed.

Datos rápidos

Aeronave: Lockheed L-2000, America’s losing supersonic transport design

Programa: U.S. national SST programme, launched 5 June 1963

Requirement: 250 passengers, Mach 2.7 to 3.0, range 4,000 miles

Competidores: Boeing, Lockheed and North American. North American was rejected early

Decisión: 31 December 1966. The Boeing 2707 was selected

Final versions: L-2000-7A at 273 ft and L-2000-7B at 293 ft, both 590,000 lb maximum weight

Motores: Four General Electric GE4 or Pratt & Whitney JTF17A turbojets, around 65,000 lbf with afterburner

Resultado: Boeing’s SST was cancelled on 20 May 1971 after Congress cut funding in March

Kennedy Started It

In 1961 President Kennedy committed the U.S. government to subsidising 75 per cent of the development of an American supersonic airliner to compete with the Anglo-French Concorde, then already under way.

The head of the FAA, Najeeb Halaby, decided not to build a Concorde competitor but a Concorde beater. Where Concorde would carry about a hundred passengers at Mach 2, the American SST would carry 250 at Mach 2.7 to 3.0 over 4,000 miles. The programme launched on 5 June 1963, and the FAA estimated a market for 500 supersonic airliners by 1990.

Boeing, Lockheed and North American responded. North American was eliminated early. The contest came down to two.

Concorde in flight — Concorde, the aircraft the American SST was meant to outclass. It carried around a hundred passengers at Mach 2; the American requirement was 250 at up to Mach 3. Photo: Wikimedia Commons.

Eight Years of Wing

Lockheed had been thinking about supersonic transports since 1958, and the L-2000’s development is essentially the story of one problem: what happens to the centre of pressure when a wing goes supersonic.

The first attempts used a tapered straight wing rather like the Caza estelar F-104’s, with a delta canard for trim. Wind tunnel work showed the centre of pressure moving so far that the aircraft would need large trim changes with speed, which means trim drag, which means burning fuel to fight your own aeroplane.

A delta wing helped and was not enough. Lockheed knew a swing wing would solve it and refused to use one, judging the weight penalty unacceptable. The engineers were prepared, in the worst case, to carry fuel purely as ballast to keep the balance right.

By 1963 they had the answer: a double-delta, with the leading edge swept 80 degrees inboard and 60 degrees outboard, carefully twisted and cambered. The sharp inboard sweep generated powerful vortices that added lift at higher angles of attack and kept the airflow attached over the controls even in a stall. The wing was only three per cent thick but so large that the aircraft could take off and land at speeds comparable to a Boeing 707.

Lockheed L-2000 rendered in Pan American livery — The L-2000 as the airlines were meant to see it. Pan American held delivery positions on both American SST designs; none was ever filled. Image: Wikimedia Commons.

The two American SST designs side by side: Lockheed’s L-2000 and the Boeing 2707 that beat it.

The Details Nobody Remembers

Some of the engineering decisions are wonderful.

The early L-2000 was to be powered by a beefed-up turbofan derivative of the Pratt & Whitney J58, the engine already proven on the Lockheed A-12 and, later, the SR-71 Blackbird. Being a turbofan it would be quieter at low speed and would not need afterburner to take off.

The main undercarriage used the same tyres as a Douglas DC-8, filled with nitrogen at lower pressures. The nose drooped for landing visibility, as Concorde’s did.

And the aircraft was designed to manage its own sonic boom. Rather than going through Mach 1 at a convenient 30,000 feet, it would stay subsonic until 42,000 feet, accelerate through the barrier, and only become audible on the ground from about Mach 1.15. It would then climb precisely, levelling around 71,500 feet and drifting up to 76,500 feet as fuel burned off. The descent was choreographed the same way.

By 1966 the design had become the L-2000-7A at 273 feet long, carrying 230 passengers in mixed class, and the stretched -7B at 293 feet. Both weighed 590,000 lb fully loaded and had a lift-to-drag ratio of 8 to 1.

31 December 1966

Full-scale mockups of the Boeing 2707-200 and the L-2000-7 were presented to the FAA. On the last day of 1966 the government picked Boeing.

The judgement was not that Lockheed’s aircraft was worse. It was that Lockheed’s aircraft was less of a leap.

“The Lockheed design was judged simpler to produce and less risky, but its performance during takeoff and at high speed was slightly lower. The Boeing design was considered more advanced, representing a greater lead over Concorde and thus more fitting to the original design mandate.”

Assessment of the 1966 SST decision — As recorded in histories of the American supersonic transport programme

Because of the JTF17A engine the Lockheed was also expected to be noisier. But the deciding factor was ambition. The government chose the riskier aircraft on purpose, because the point of the programme had never been to match Concorde. It was to humiliate it.

And Then Boeing Built the Lockheed

Boeing’s winning 2707 had an advanced variable-geometry wing, the swing wing Lockheed had rejected as too heavy.

Boeing discovered Lockheed had been right. The mechanism was unworkably heavy, and Boeing abandoned it, replacing it with a fixed delta wing broadly similar to Lockheed’s, though with a tail. The aircraft that had won on the strength of its variable geometry no longer had any.

Ticket Through the Sound Barrier, the 1966 film made to sell the American public on supersonic travel.

It made no difference. Congress stopped federal funding on 24 March 1971 and the programme was cancelled outright on 20 May. No American SST was ever built.

“The FAA estimated that by 1990 there would be a market for 500 supersonic transports. Fourteen Concordes entered airline service, and no American supersonic transport was ever completed.”

The forecast against the outcome — What the 1963 programme promised, and what actually happened

Boeing’s own promotional film for the 2707, the aircraft that beat the L-2000 and was then cancelled.

The Aircraft That Was Right

There is a tidy irony here that aerospace engineers enjoy more than accountants do.

Lockheed spent eight years working out that a fixed double-delta was the answer and that a swing wing was not worth its weight. The FAA marked that down as insufficient ambition. Boeing won with the swing wing, then threw it away and adopted a fixed delta, by which time the aircraft had lost the argument that won it the contract.

What survives is a set of drawings, a handful of photographs of a full-scale mockup in a Lockheed hangar, and an aeroplane that was quieter, cheaper and easier to build than the one that beat it. Being sensible has rarely been a worse career move.

Sources: Walter J. Boyne, Beyond the Horizons: The Lockheed Story; René J. Francillon, Lockheed Aircraft Since 1913; Flight archive articles on the United States SST contenders, 1964 and 1966

Preguntas frecuentes

What was the Lockheed L-2000?

Lockheed’s entry in the U.S. government competition to build an American supersonic airliner in the 1960s. It was a double-delta design intended to carry around 230 passengers at up to Mach 3. It lost to the Boeing 2707 on 31 December 1966 and was never built.

Why did the Lockheed L-2000 lose to the Boeing 2707?

Because it was considered less ambitious. The FAA judged the L-2000 simpler to produce and less risky, but slightly inferior in take-off and high-speed performance and likely to be noisier. Boeing’s design represented a greater technological lead over Concorde, which was the stated purpose of the programme.

Did the Boeing 2707 ever fly?

No. Congress stopped federal funding on 24 March 1971 and the programme was cancelled on 20 May 1971. No prototype was completed, so neither American SST design ever flew.

What was unusual about the Lockheed L-2000 wing?

It was a double-delta with 80 degrees of leading-edge sweep inboard and 60 degrees outboard, twisted and cambered, and only three per cent thick. The sharp inboard sweep generated vortices that added lift at higher angles of attack and kept airflow attached over the control surfaces even in a stall.

Why did Lockheed reject a swing wing for the L-2000?

Because the weight penalty was judged unacceptable. Lockheed knew variable geometry would solve its centre-of-pressure problem but preferred a fixed-wing solution. Boeing won partly on its variable-geometry wing, then abandoned it as too heavy and adopted a fixed delta similar to Lockheed’s.

How fast was the Lockheed L-2000 meant to fly?

Mach 3, with a range of 4,000 nautical miles and a service ceiling of 76,500 feet. It was designed to stay subsonic until around 42,000 to 45,000 feet specifically to reduce the sonic boom heard on the ground.

Was the American SST bigger than Concorde?

Considerably. Concorde carried roughly a hundred passengers at Mach 2. The American requirement was for 250 passengers at Mach 2.7 to 3.0, and the final Lockheed L-2000-7B was 293 feet long with a maximum weight of 590,000 lb.