As you know, I work for Interoute. Our network connects 78 cities in 22 countries across 47'000 kilometres of lit fibre. Such a large and dense network allows us to have extremely competitive prices. However, fibre optics are something very fragile, and there are numerous events that might cause a break (civil work, natural disaster, etc).
People usually think repairing such a fibre break is easy. Pictures below have been taken during an extended fibre break few months ago, over a river between Leipzig and Prague, whereby a 2500m long section had to be re-routed to avoid as many splices as possible along the route.
This is an example of the challenges we face with such "major outages", especially with our very aggressive SLA.