The only thing liquids could is if X takes a liquid, say alcohol or other flammable liquids, spray and light up in a seconds. Not sure how the physics work with

The only thing liquids could is if X takes a liquid, say alcohol or other flammable liquids, spray and light up in a seconds. Not sure how the physics work with the plane's config but that may be a problem. As for the rest, he /she will have to deal with dozens or hundreds of passengers and a knife will just not do.