Carrier reliability and diversity

The air line reservation system Galileo had significant problems

Excerpt from Reuters:
"The outage began about 8:30 p.m. Mountain Daylight Time on Wednesday
and lasted until 10:55 a.m. MDT on Thursday, said Beth Tennis, vice
present of enterprise networks for Quantitude, Galileo's Denver-based
networking subsidiary. It affected three of the four T-1 high-speed
data transmission lines supplied to Galileo by AT&T Corp., said
Beth Tennis"

Although I've found AT&T has the highest reliability of all the carriers
I've used. Redundant links from the same carrier frequently have a
common vulnerability, the carrier. For things which absolutely can't go
down, I assume even AT&T will have occasional problems. Personally I
used AT&T Worldnet and Earthlink, alternating depending on who had a
problem. That's high praise for me.