Remember when the Russians shot down a Korean Airlines 747 accidentally, which was 4 degrees off its course and flew over Russian Airspace. Migs shot it down with two missiles, one hitting the tail and one hitting the left wing, everyone on board died. The CIA also owns some 747 aircraft. The Russians thought it was a Spy Plane. The CIA does have such spy planes and so even though the interception and demise of that flight sparked an international incident, the Russians issues at the time were not without merit.

http://news.bbc.co.uk/onthisday/hi/dates/stories/september/1/newsid_2493000/2493469.stm

The Boeing 747 is just about the biggest and probably for sure the best possible platform for an on-board laser. The concept is a good match of the latest and greatest technology and the worlds most stable platform, even entrusted to carrying the space shuttle.

On Board Laser 747 Concept:

http://www.ast.lmco.com/SSC/images/gallery/missileDef/airborne_laser/abl2_lo.jpg

One possible advantage to an airborne laser missile defense system is that since it looks like an airliner it may not be easily detected as a military target, however at the same time once it uses its weapon to defend against the first ICBM missile inbound to the US it will have given itself away and all other nearby 747 or large four engine airliners are now at risk. It is for that reason that we must find a solution to protecting innocent human life on airliners from mistake and identity. A 747 carries many passengers and like we saw many years back with the Russians taking down a civilian 747 we need not repeat that tragedy.