http://www.snopes.com/politics/crime/skyterror.aspAccording to snopes:
The expiry date indicates the date after which that visa may no longer be used to travel to the U.S. A valid visa does not in itself grant the holder the right to enter the U.S., but merely authorizes the holder to seek permission to enter the country from a U.S. immigration officer. Only that officer can approve or deny entry, and it is that officer who will inscribe on that visitor's I-94 Arrival-Departure Record the date by which the traveler must leave the country. The same visa can be used by its rightful holder on multiple occasions (as in the case of someone who travels frequently), but each entry has to be approved by an immigration officer who will on each occasion make a determination as to when that visitor must leave. My co-worker claims that those Visas were invalid, the musicians were rude to other passingers and everyone was afraid to stop them on the plane. And because of the 'expired Visas', everyone on that plane had the right to worry about terrorism and these Musicians should have been kicked out of the country.
I'm not too up-to-date about his whole Visa stuff and how it works (well unless it's the credit card kind). Help me understand so I can explain to my co-worker that this was nothing more than mass hysteria
BTW found this picture at Salon: