The large ZipLoc bags doled out to pax at LHR are a very effective method of dealing with suspicious looking/acting fellow passengers after becoming airborne. Placing the bag over the suspect's head and "zipping" it ssecurely beneath his/her chin can be both an effective interrogation tool, as well a useful method for extremely prejudicial (to reuse a 60s phrase) termination.

Of course, enlisting fellow pax to sit on the suspect's/suspects' hands and feet comes in handy and reduces flailing about.... As with morphine styrettes, rarely is the genuine Tom Ridge/TSA duct tape available when you need it most.