With regard to pressure vessels, the B777 has 14 tyres each pressurized to 200+psi. There's a fair bit of stored energy for you already.
If you filled the tyre with water, and were to rig up some means of passing hot air from a fire through the wheel hub, water in the tyre would eventually boil. Don't try this at home!
Any sealable metal, ceramic or hard plastic container filled with fuel and oxygen has the potential of making a land or claymore mine if you use a battery and a pressure switch to create a spark inside. Alternatively, you could trigger them remotely, as there is no shortage of wire in an airliner. Your Iraq veteran will have seen IEDs or been briefed on them to know what is needed.
If you can find where uni-directional carbon or glass fibre is used in the structure, you have potential longbow material, There are 10 tons of Carbon fibre in a B777, so some of it should be useful if you can cut and shape it.
This may be a useful resource for who supplies what for the B777:
Boeing 777 - program supplier guide