At the time of cancellation in 1971, the B2707-300 (the tailed delta) had some 120 options, compared to 74 for Concorde.
Most airlines who had optioned Concorde also optioned B2707's, including BOAC and AF.
Think of the 2707 as an SST 747, and Concorde as a 767.
There was much surprise when Boeing got the SST contract in 1966, Lockheed, with the delta L2000 had been firm favorites, not least because of their supersonic experience.
The US SST began life in 1963, not long after Concorde was launched, JFK was warned that in the 1970's the US could lose their technical edge if a programme was not started, the FAA would run it.
Boeing's first design was the 2707-100, a swing-wing design powered by 4 70,000lb GE4 turbojets, a capacity of 230-300 pax and Mach 3 cruise, though that was soon reduced to Mach 2.7, nonetheless, it had to be bigger and faster than Concorde.
Soon Boeing went to the -200, where the huge engines were mounted on the a large tailplane, a bitter Lockheed engineer commented 'I guess they had to put them there to stop them from burning the tail off!'
This would be an extremely complex aircraft, the VG wings having leading-edge and triple-slotted trailing edge flaps, a droop nose like Concorde, but much more complex, some airline pilots were already expressing concern.
But tests with models were showing that the wing would need strengthening, on an already very overweight design.
It was looking like the aircraft could only get airborne it it had no payload, pax or baggage.
A major redesign was in the offing.
The variable intake system was also a cause for concern, but Boeing ploughed on, this was after all the future of civil air transport, so much so the 747 design had a raised cockpit, as it was expected to soon be replaced by the 2707 on mainline routes, so it was prudent to make the 747 easily convertible to a freighter.
By now, service entry had slipped from 1972, to 1974 and so on, but Concorde had it's share of problems so the 2707 coming late to market was not a concern, it would have the bigger share of orders after all.
In 1969, Boeing finally gave up on the swing-wing, and went for the 230 seat Mach 2.7 tailed delta -300. It at least looked more practical, not to mention simpler to build and operate.
Service entry in 1976-78, assuming a 1972-73 first flight.
Speed was not to be the only innovation, the 3 crew flight deck would have some cathode-ray tube displays, cutting down on the the bewildering array of electro-mechanical instruments.
But by now, concerns about noise had restricted all SST's to mostly overwater supercruise.
As air travel exploded in the late 60's more and more people became affected by aircraft noise, SST's looked like a bad idea to many.
The fact that 90% of the 2707 was being funded from tax $ made it a target of many right-wingers in the US, who saw it a 'socialist' and 'un-American', what a strange alliance that was, right wing republicans with people they'd call 'tree-huggers'!
But some like Senator Barry Goldwater, defended the SST vigorously.
1970 saw the 'Earth Day', the first really big environmental campaign, SST's were seen as a polluting, noisy threat to the well-being of both the Earth and it's inhabitants.
Boeing had their own problems, the Mach 2.7 specification required the use of titanium as the primary structure, very expensive, difficult to work with, (aluminum melts at Mach 2.6), plus massive challenges in environmental control systems etc.
Making Concorde work at Mach 2 was hard enough, the mind boggles at the challenges Boeing engineers faced.
So more money, more time, the SST ban overland was almost as bad for the 2707 as it was for Concorde, the 2707 would only have a few hundred miles more range, non-stop Trans-Pacific was out.
In 1971, time and money ran out, Congress voted, by a majority of one, to stop funding the programme.
As much cash had been spent as the UK contribution to Concorde up to 1982.
Airlines were in a slump, Nixon had to slash spending while remaining popular, (the US was still in Vietnam).
The 2707, along with the space programme took the hit, but fears of excessive layoffs in aerospace and the political implications in vital states like CA, led to the Space Shuttle programme being approved a few months later.
Could the 2707 have been at least a technical success? (The 1973 oil price hike would have done for it in the same way as Concorde sales wise).
Without a prototype flying it's hard to say, it would have been an immensely complex and expensive aircraft to maintain and operate, (basically Concorde X2).
Boeing got the pax capacity right, but not much else, imagine 4x70,000lbs reheated engines on take-off, nearly twice as much as Concorde.
IMHO Lockheed should have got the contract, with a sound design from the start they would probably have got a prototype in the air, at less cost, before the major anti-SST campaigns started.
So even without a service entry (it still would have had all the environmental problems) the US would have had a very valuable research tool.