And also because we are unlikely to be talking about GBAD being used against a large aircraft - that's the job of the Typhoon boys.
Assuming the govt is really worried about hijacked airliners:
They may be deactivated but are there absolutely none in storage somewhere?
Are there equivalent missile systems we can buy off the shelf?
What about a small scale production run?
IMVHO the probability of a hijacked airliner is miniscule and made even smaller with passenger profiling and plainclothes armed sky marshals.
If any problems happen I expect them to be of the "shoot-and-scoot" variety: snipers with high powered rifles or mortars causing a stampede, IEDs left around, suicide bombers or someone driving around with a portable nerve gas factory (the sort of nerve gas whose symptoms only develop a few months after exposure).
You want to procure, introduce into service and train soldiers in the use of a brand new missile system within two or three months?
Personally, no. For the following reasons:
1) I don't think a hijacked aircraft crashing into a stadium is a likely possibility, given the additional vigilance in the civil air transport sector we've seen over the years. For all we know there may already be plans afoot to have plainclothes armed sky marshals aboard flights to London. I would surmise that the conclusion among terrorist circles is that airliners are now hard targets.
2) Realistically if a civilian airliner is to have a chance at crashing into a stadium it would have to be hijacked while over London, so that the response time is reduced and IF the govt. decides to shoot it down, it will cause major collateral damage anyway which will be blamed on the govt (win-win for terrorists). So it is feasible to have armed skymarshals and passenger profiling on a small scale only for flights to/from London.
3) The terrorists have other lower cost/risk options.
4) The terrorists have softer targets.
5) The reasons you mentioned. Our Treasury is running on printed money.
Of course nobody dares say that the lowest damage option is simply to allow the a/c to continue on course and land in said Olympic stadium.
What's the relative value of a few thousand overseas tourists and overpaid corporate guests vs the local population? And it'll help with "legacy" by levelling the site ready to build all those houses on it.
Steady fella, outside of Russian owned Mayfair masses of barbecued civ.pop entirely acceptable collateral damage if there is the slightest risk to the BP or BAE enclosures. As a concerned shareholder I'm sure Dave will do his duty to UK PLC and bring any suspect 747 crashing down into the densest possible concentration of orc like cockney mouth breathers rather than a single cooperate canapé being disturbed.
Exactly what situation would these missiles be used in ?
Hijack maybe ? Hardly a good outcome for the passengers
9/11 situation ? Shoot the plane down so it drops somewhere other than its intended target
Single seater plane loaded with SAM's and a mad mullah waiting to get laid by his 70 virgins ? ( Is it 70 ? )
Or blowing the alien mothership out of the sky
They should have had the olympics in Luton, any terror events in that area would be doing us a massive favour. and would be an own goal for Allah and sons. As for bombs and such like in London they would be lucky to hit a native British person in any event, they should come up North where there is a chance of hitting an actual British person whos parents lived though WW2, but make it quick johnny foreigner is already launching an all out attack on our housing, medical and benefits services.