Clive wrote:

Concorde....

Both European airlines operated demonstrations and test flights from
1974
onwards. The testing of Concorde set records which are still not
surpassed; it undertook 5,335 flight hours in the prototype,
preproduction, and first production aircraft alone. A total of 2,000
test
hours were supersonic. This equates to approximately four times as many
as
for similarly sized subsonic commercial aircraft.

Clive

And the ratio of hours of revenue flight for the two are what then?
And when you combine the two, the ratio of revenue flight hours to
test-flight time is what?

Concorde had been the safest working passenger airliner in the world
according to passenger deaths per distance travelled, although the Boeing
737 fleet acquires more passenger miles and service hours in one week than
the Concorde fleet acquired in the course of its entire service career.

Which is sort of the point...actually one of many points against
Concorde. According to AirSafe.com, The 747 flew about 16 million
flights over the course of its continuing career, and in that time
suffered 28 fatal events. Concorde suffered only one, but amassed a
much smaller flight record - only 90 thousand - meaning that we'd have
to multiply the number of fatal events by 180, then further factor the
much smaller passenger capacity of the Concorde to get a better idea of
what Concorde could have done were it actually judged by the same
standards as unglamorous subsonic jobs that actually move the vast bulk
of airline passengers and generate revenues for their operators. This
is ofcourse putting aside the possibility that fatal-event numbers
would not remain proportionate to the number of flights in the event
that operators would try to get more flights out of Concorde.

The crash of the Concorde was the beginning of the end of its career.

Good enough?

If you really think that it took the crash of Concorde to begin the end
of its career, then that's probably good enough for you. For me, the
fact that Concord made only a negligible dent on air travel, carried
only the deepest-pocketed passengers - if anybody- and laid no ground
for a successor.