The Concorde seems like a logical progression if you naively follow the trend line of advances in transportation from sail and horses to steam ships and trains to automobiles and propeller aircraft to high speed rail and jets as being one purely of increasing speed. And certainly speed is a major factor in all of those things, but in particular with jet travel one of the key benefits is not just speed but reliability and service life. With a well designed and well taken care of commercial jet you can turn around between typical flights with little more than just refueling and reboarding. Passenger jets have a tremendously favorable duty cycle precisely because of the characteristics of jet engines, this is a big reason why they are economical to operate for long distance travel, but the efficiency of the jet engine at sub-Mach cruising speeds also helps tremendously.

The development of the Concorde (and the planned but cancelled development of the Boeing SST) follow this putative trend line of increasing speed to the logical next step in the mid 20th century: supersonic speeds. But once you get into the details a lot of problems arise very rapidly. Technologically building the Concorde proved to be a lot more challenging than was initially imagined, resulting in ballooning development costs (by about 20x) and per-unit costs which priced it at many times that of other passenger aircraft. Despite its high speed it used a prodigious amount of fuel to supercruise, with about half the efficiency of the no longer cutting edge Boeing 707 and even less compared to the next generation of planes coming along in the '60s like the DC-10. These factors together meant that even if a Concorde had the same level of reliability and downtime as a competing jet liner it would never be as profitable at equivalent ticket prices for equivalent routes. The only way to make money with the Concorde was by charging a premium, and a big one. On top of that because the Concorde was such an early generation of supersonic plane it did not have very good mitigations for sonic booms, which forced it to be restricted to supersonic flying over the oceans almost exclusively. These factors caused orders for the Concorde to dry up and it became apparent pretty quickly that the program could not be sustained as a commercial enterprise regardless of the technical achievements made.

The British and French aerospace companies that had collaborated on the development of the Concorde saw this future and curtailed further manufacture of the vehicle, selling a small run of vehicles to the British and French air travel companies (British Airways and Air France) for a nominal amount, writing off the development expenses as a sunk cost. Without having to pay the full cost of the planes it became possible to operate them as a luxury service without necessarily taking a loss. Operating fast trans-Atlantic flights for wealthy individuals or important business travelers allowed the airways to charge high enough prices to make up for the expenses of operating the planes (not just the fuel but the special maintenance and the pilots). Even so the limited production run of vehicles and the smaller market of customers meant that such business would only ever be a sideshow for the operators.

But the Concorde managed, through the oil shocks of the '70s and the economic and geopolitical mess of the '80s and '90s people kept buying Concorde tickets and the operators kept flying them. The Concorde service was perceived as a prestige brand, not just because of the level of service and exclusivity but also because of its seemingly unblemished safety record. Part of this safety record is just a matter of convenient amnesia, there were a few worrying incidents that occurred on Concorde flights through the years, but none caused loss of life or injury so they didn't receive a lot of press and it's not like your average passenger in the '80s was going to do the work to meticulously investigate the safety record of the plane, aside from the difficulty of doing so back then before so much information available was available on the internet. Mostly it just benefitted from the statistics of small numbers.

At the turn of the 21st century air travel faced a bit of a rocky outlook due to the popping of the cot-com bubble which started in early to mid 2000, probably one of the worst times for the Concorde to have a showy and dramatic disaster with huge loss of life. The loss of Air France 4590 just after takeoff dealt a huge blow to the perception of Concorde as a prestige brand with a flawless safety record. As the dot-com downturn turned into a proper recession air travel across the board took a hit, and the Concorde even more so due to the sullying of its image. The year after 9/11 devastated the global air travel market. A few years later Airbus decided to stop making spare parts for the Concorde, and both Air France and British Airways decided to hang up the towel at that point.

The unfortunate crash of the Concorde brought home some of the realities of the safety of the vehicle. The pre-crash perception of the Concorde was as an unbeatable technological marvel, but many aspects of the vehicle made it potentially more dangerous to fly. For one, the fineness ratio of the plane required to slip through the air reasonably efficiently at Mach 2 also meant that it had a comparatively high stall speed (and thus high takeoff and landing speeds), it also meant that at takeoff and landing speeds it had a very low glide ratio. A 747 has a glide ratio of about 15:1, which means that with no engine power whatsoever a 747 can glide a distance of 15x its altitude. That means every 70 meters of altitude the plane has it can glide for a full kilometer. The Concorde's glide ratio was just 4:1 though, meaning that it could only glide 4x as far as its altitude without power. These two facts together are why surviving a complete loss of engine power in the Concorde is much less survivable than in a modern jumbo jet. In a passenger jet the vehicle has a glide ratio to be able to make it to other destinations, which could be other airports or any suitably flat surface. There have been numerous times when aircraft have been ditched on water or in the wilderness and have managed to save many passengers. For example, Varig Flight 254 (a 737) ran itself out of fuel over the amazon and crashed into the rain forest, with 42 of the 54 passengers and crew surviving. This was possible because the glide ratio allowed for choices in picking the safest place to land and the lower stall speed allowed for less energetic conditions during the crash. A Concorde is constrained by its low glide ratio to land wherever it can, and its higher stall speed means that any crash landing or ditch is much less likely to be survivable due to greater energies.

And, of course, the big issue was the tires. The Concorde had a series of incidents involving tire failures during its service life, some of them potentially very serious including punctured fuel tanks. This was directly due to the higher takeoff speed required for the aircraft, which also necessitated higher tire pressures. That combination resulted in the potential for tire failures to propel fragments at a speed sufficient to penetrate key parts of the aircraft including the engines, wings, and the fuel tanks. And that's exactly what happened on flight 4590 when the Concorde's luck finally ran out. The aircraft ran over a piece of metal debris on the runway which caused a tire to burst, the shrapnel from the exploding tire hit the underside of one wing and caused a fuel tank to rupture due to hydrodynamic pressure. This was followed by a complete loss of power in two engines (though one slowly recovered) and the ignition of the leaking fuel (which would cause cascade effects within seconds). The vehicle was already too fast to abort a landing so they had to take off, but with an engine out and the landing gear unable to be retracted they were unable to gain much speed or altitude and they crashed only 6 km from the end of the runway after the single remaining left engine surged out of control.

The investigation after the crash revealed that this kind of failure was something that the Concorde was somewhat uniquely vulnerable to, and had many close calls with in the past. It was only after an extensive process of analysis and fixes to mitigate that particular failure mode that the Concorde returned to flight at all, but this brought the vehicle back into service only two months prior to 9/11. Whatever remnant had existed of the Concorde's mystique was not enough to support the high ticket prices it needed to continue operating and as it became increasingly unprofitable to operate and increasingly antiquated with no possibility for updates it was finally discontinued.