This happened a few days ago, and it is looking like a lone-wolf suicide attack that is not terrorist related. The bomber's motivations are still unknown, but there is some discussion about it being a targeted attack against AT&T. One thing is known - a single well placed explosion shut down air traffic control services at Nashville International Airport, and took out phone, internet and 911 services across middle Tennessee and parts of Kentucky, Alabama and Georgia.
To their credit, AT&T responded quickly and most outages were mitigated within hours. But consider this - a deliberate, coordinated attack against just two or three well selected communications nodes - AT&T, Verizon, Comcast or T-Mobile - has the very real potential to knock out regional communications and shut down services for an extended period of time. No cellphone, no internet (which carries a lot of voice-over-internet (VOIP) traffic), no landline comms.
On this blog I spend a lot of time discussing the very real and very likely communications threats posed by hurricanes, tornados, wildfires and earthquakes. Terrorist attacks are far down on my list, mainly because the US government does a good job of tracking coordinated terrorist groups like ISIS, and we generally know more about their attack plans than they do themselves. But every once in a while fate says "hold my beer" and hands us something like the Nashville attack. One bomb, millions without communications.
An alternative communications plan isn't just an interesting 'what-if' intellectual exercise. It's a necessity. Be ready.