[PapaBear3625]

A little bit of googling finds that there are at least two commercially-available binary explosives that fit the profile of what this guy was doing.

With both of them, you have a liquid component and a solid powder component, both inert until the two components are mixed. Once mixed, they can be set off with a blasting cap (which looks a lot like a firecracker).

[njslim]

Remember Arson detection class

Instructor took oxidizer (potassium permanganate) and
dropped glycerin on it. Ignited about 30 seconds later

Showed same thing with brake fluid and HTH (pool chlorine)

Plenty of common things work - dont need sodium or other
hard to procure metals

[csvset]

Interesting. The Islamic terrorists have a thing about chemical bombs and airliners.

Another possability is Thermite

Sitting next to the wing/fuel tanks. Hoping for a catastrophic fire perhaps?

It can be ignited using the reaction between potassium permanganate and glycerol or ethylene glycol.