The reason I know this is terrorism is simple. Bin Laden said in his tape that there would be more planes lost. I'm not a statistician, but I know the odds that an AMERICAN Airlines airliner flying out of New York on Veterans Day would be the ONE plane to have a fatal "accident" out of all the planes to fly in the world yesterday are absolutely astronomical.(Not to mention it was a flight with enough fuel for some 1500 miles). We just need to know how it was done and who to arrest-- and which terrorist-abetting regime to go after next.
Consider a shooting scenario, the intention being to cause a catastrophic failure of an engine on take off leading to a crash.
I would envision a (hypothetical) runway sniper using a van soundproofed on the inside with cheap foam mattresses. The exact shooting position would be determined in advance so that a shooting chair and rifle rest could be set up inside the van in advance. The shot could be taken through a removed small rear door window.
The shooter would drive to his pre-determined road side parking place, get in the chair, and use his 12 or 20 power off-the-shelf scope to observe the jets as they turned into the take off position. Seeing the big twin engine jet with the American Airlines logo side-on, he would have plenty of time to settle in for his one and only shot. He would pick a twin engine, to maximize the chance of causing a crash after shooting one engine.
As the jet races down the runway straight towards him, the shooter holds his crosshairs just above the center of the 12 foot diameter engine. As the wheels come off the tarmac, he fires. Even a .30 caliber slug through the engine turbines could cause the massive failure he seeks, a .50 caliber would ensure it.
If the jet lands right on him, he screams "Allah Akbar" with a big grin on his face, and goes to collect his 72 virgins right away.
If the jet crashes beyond him or not at all, he gets back into his driver's seat, and checks his map for the route to Logan, Dulles, O'hare or Miami International.
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So why do I go to the trouble of pitching this hypothesis? Because even if there was no sniper at the end of the runway at JFK today, there might be next week. The national guardsmen standing around looking scary in the terminals doing nothing but providing pseudo-security PR, should instead be patrolling the airport runway approaches with their M-16A2s, looking for my hypothetical but entirely possible (even likely) snipers.
What are they doing in the terminals anyway? Looking for hidden boxcutters with their X-ray eyes?