94
Americans wake to widespread cellular outages, cause unclear
(www.theregister.com)
This is a most excellent place for technology news and articles.
Unlikely. The most likely cause is that it was caused by a misconfiguration, like someone typo'd a line in a file somewhere, which then propagated outwards when everything downstream got the faulty update.
If it was a solar flare,or cyberwarfare, it would be more indiscriminate, rather than targeting a specific vendor's hardware or a single network.
Edit: Sure enough, it was a botched update.