Yeah? What would it cost? I have no clue.
As much as £100 million in todays money; but virtually impossible anyway:
"Question 22: Finally, THE question - will any of the remaining Concordes ever fly again?
While it can be said that you should never say "never", it is safe to say that, unfortunately, it is extremely unlikely that a Concorde will ever fly again. This is due to many factors:
Of the flight crews that flew the aircraft, those that didn't retire and are still actually flying no longer have a means to keep their licences current as the facilities required to re-certify them (i.e. - a CAA approved simulator) no longer exist.
All spare parts were either scrapped or auctioned off when Concorde retired. Those that were auctioned off are no longer deemed to be airworthy since leaving the strict control of British Airways' and Air France's bonded stores and therefore could not be used. In addition, much of the infrastructure needed to make spares has gone and many of the hundreds of OEMs (original equipment manufacturers) that manufactured those parts and have design authority over them no longer exist.
The facilities and equipment for servicing and repairing all parts of Concorde's airframe, engines and systems no longer exist.
There are no longer any licensed engineers who would be able to a) return a Concorde to airworthy condition, or b) service/maintain the aircraft to keep it airworthy. This is because all the engineers who worked on Concorde over the years have now either re-trained on other aircraft types, or they have retired. Either way, their licences expired a short time after Concorde's retirement.
Of the remaining Concordes, none are in flying condition anymore. Some of them were approaching major scheduled servicing prior to being retired and this would have to be carried out before the aircraft would be allowed fly again. However, such work would no longer be possible because of the factors outlined in the previous 3 paragraphs. There is also the fact that it is extremely unlikely that any of the museums who have a Concorde would be willing to give up their prize exhibit.
It is often asked why many older aircraft types are still flying today but Concorde isn't. However, it must be taken into account that Concorde is an order of magnitude more complex both to maintain and to operate than aircraft such as a Spitfire, Lancaster or even a Vulcan which are all very basic in comparison. Concorde has scores of computer controlled systems and sensors that mean, unlike most heritage aircraft, it would be impossible for it to be maintained, operated and kept airworthy by a handful of enthusiasts with basic facilities.
Some people may of heard stories of one of the Air France Concordes being kept serviceable. Unfortunately the word "serviceable" can be rather misleading. In this case it simply means that they have maintained some of the electrical and hydraulic systems to a sufficient extent that allows them to connect ground-power from the museum to the aircraft and do things like illuminate the cockpit instruments and move the droop nose up and down occasionally for museum visitors. Like all other remaining fleet Concordes, this one in France hasn't flown since 2003 and, in reality, is far from being in a position to do so.
It could be argued that many of the issues listed above could be solved by money. However, how much money? Some people closely involved with Concorde have been quoted saying that £10-£15 million should be sufficient. This may well have been the case in 2003 but a long time has passed since the last flight and now that the Concorde support chain has been disbanded and the spares holding disposed of, the amount needed would be astronomical - possibly over £100 million.
There will no doubt be differing opinions on this but my view would be that spending such a vast amount of money would be totally unjustifiable just to get one aircraft airworthy for a handful of air shows a year - even if it is Concorde! It is also necessary to bear in mind that these figures just relate to the money needed to get a Concorde back into airworthy condition. The costs of on-going service/maintenance and flight operations would all be in addition to this.
Concorde no longer has a Certificate of Airworthiness. This is a document issued by the Civil Aviation Authority (CAA) and is a legal requirement for all civilian aircraft types before they are allowed to fly. Concorde's was withdrawn by the CAA soon after its final flight in 2003. For there to be any hope of Concorde's certificate being re-instated it would be essential to have the support of the manufacturer. Unfortunately, Concorde does not (see the following paragraph).
And the real show-stopper - Concorde was originally manufactured by BAC of the UK and Aerospatialé of France who both later became part of the Airbus consortium. Unfortunately, Airbus have repeatedly stated they have no interest in participating in returning Concorde to the skies. Airbus was the key supplier in the Concorde operation. Not only did it build Concorde, it specified and controlled the maintenance programme and was the end supplier of the parts that made it fly. Without their support it doesn't make any difference how much money is made available - the whole idea literally is a non-starter.
All this makes for depressing reading for all Concorde fans and while most people would love to see her flying again (me included!), the sad truth is that you will now almost certainly only ever be able to enjoy Concorde in a museum".