CNN reports an airborne anti-misslle defense system being tested on FedEx planes.
http://www.cnn.com/2007/TECH/01/16/airline.anti.missile.ap/index.html
Anyone catch that the part where they say the MD-10 is a freight variant of the DC-10? That’s news to me… 
MD-10 is a Boeing/MD retrofit for FedEx.
Yes, but that doesn’t mean it’s just a freight variant. That is not the purpose of the upgrade from DC to MD. There are DC-10 freighters as well.
So when do we stop preparing for the possible. If it is possible to hit a plane with a missle, then we spend money to defend against that possibility. It is also possible with the use of a proximity fuse to get an explosive shell near an airplane to disable it ( tech from 1944-45). Do we counter that threat.
What about a more probable threat of someone walking through the gates of an airport, or improvising a device and walk it through security.
It seems that our reactions are always inverse to the real threat.