In 1974, intelligence reports suggested that terrorists had smuggled SA-7's into Europe, security was beefed-up, including occasional troop deployments around airports such as LHR.
Years ago, I read a novel, (published in 1977), called 'SAM-7', where Arab terrorists used an SA-7 against a DC-10 on finals to LHR, firing from the top of a tower block, the aircraft crashing in central London.
The IRA tried for a long time to get SA-7's, and came very close to getting the US equivalent missile, Redeye. (From their many supporters in the US).
Finally, it appeared the Libya gave the IRA some SA-7's in the mid-1980's, as they were unlikely to use them against civil airliners, British military helicopters in N.I. and transport aircraft were fitted with countermeasures, as were V.I.P. aircraft generally.
If Al-Queda smuggled, and used, a US supplied Stinger missile against an airliner, imagine the political ramifications, a US weapon supplied to extreme fundamentalists by the Reagan administration, used against a US civil airliner. (Stinger is by far the most effective of these class of IR-guided, shoulder-launched missiles).
Thanks to Reagan and Oliver North, similar weapons supplied to Iran, (to get US hostages out of Lebanon), were used in the 'tanker war' in the Persian Gulf in 1987-88, one shot down a US Marine AH-1 attack helicopter, And North an ex-Marine too!
What countermeasures to take? The large areas around take off and approach paths that would have to be secured, and the number of airports in the US, would make for a security nightmare.
Taking all this into consideration, you'd think the Bush administration, being so nostalgic for the Reagan years, (tough old Ronnie? Terrorist appeaser more like) would keep quiet about this.
Unfortunately, this sort of idea has probably been an Al-Queda, and other terrorists goal for many years.