I don't think I'm buying this.
Even if you could secretly get the ingredients for thermite on board it is still very difficult to ignite the magnesium needed to set the mixture off. Unless I am mistaken you cannot ignite magnesium with, say, matches or a butane lighter. Every time I've seen it done it is performed with a high temperature torch such as MAPP gas.
And even if you were to get the mixture ignited it would burn through the cabin floor and the fuselage so quickly it would almost certainly not cause an airframe failure. It's not as if it could get to the fuel tanks. It couldn't damage the engines and it would be a lucky thing (or unlucky thing) if it were to sever a control line. Plus, a lot of controls are redundant and have backups. Sure, the cabin would be full of smoke but as soon as it burned through the fuselage that would be the end of it and the suction from cabin depressurization would remove a lot of the smoke.
I just don't see this as a surefire airplane killer. At least not the way a bomb is where there is massive damage that, combined with flight velocity, rips the plane apart.
One thing I am wondering about is the motive for releasing this info. Could it be that this is a threat that they have heard being discussed by the enemy? Or is it just another one of the BO admin's distractions? DHS looking to prod the congressional Republicans to fund the agency with no messy amnesty stuff?
