British troops at Heathrow are apparently trying to stop another SAM attack on a passenger jet a la Mombasa last November. They're definitely taking this seriously - according to the Guardian, they were even considering closing Heathrow, which is the world's busiest airport.

The article mentions the Mombasa attack, but it doesn't clear up the issue of why that attack was ineffective. There were widespread rumors at the time that the airliner operated an anti-missle system, but I don't see how that's possible - according to this article, El Al is the only airline to operate such a system, and the flight in Mombasa was Arkia Airlines. The article does suggest commercial airliners are harder to hit than military aircraft, because they don't generate as much heat.