Ok. I just read Null and Void's point.
I take back my pointing out that there are call boxes in the tunnels.
That, and where would FLT 93 have ended up if the current ban on cell phones had been in place on 9/11? The passengers would have blissfully sat there assuming they were under the old rules:
The plane is hijacked. Flown somewhere. Threats are made. Demands are voiced. Compromises reached. Pretty much everyone goes home with an interesting story to tell their grandkids.
Would we have lost Congress? The White House? Or what?