I found that some 777 have optional O2 tanks for supplying PAX masks. If I mix that with some spilled fuel from the APU feed, maybe that combo would go "boom" enough. I know that the fuel on the plane is more like kerosene - but mix it with some O2 and I would guess it gets a bit more violent. I found a "Flammables" document on 777 for emergency responders - good document to show where interesting things are.