Supposedly al-Modadi got up to use the bathroom around 30 minutes before the flight landed; he was in there for awhile and when he came out an air marshal smelled smoke.
When the marshal asked him what he was doing in the bathroom, al-Modadi supposedly said, “I was trying to light my shoes on fire.”
In fact, he might have simply been having a cigarette and responding sarcastically, which I guess the marshal didn’t pick up on.