It is far from unimaginable that there would be pairs of a couple of terrorists each with a SAM between them who coordinated their attacks to hit aircraft at LGA, JFK, LAX, SFO, MIA, SEA, etc. pretty much simultaneously. That would be exactly the kind of statement they would want to make.

They could be in barges off the coastlines, or in trucks parked near airports, or whereever. The availability of the weapons is not a question or issue... yet we focus on shoes and lighters