You're assuming the failure rate is related to the number of flights. With 2 failures in 20 years there's not really enough data to extrapolate. And remember t

You're assuming the failure rate is related to the number of flights. With 2 failures in 20 years there's not really enough data to extrapolate. And remember this wasn't a complete system outage - it affected 50% of flights, a degraded service. In comparison the vast majority of startups that HN people work in will be lucky to last 2 years. In the last 10 years Gmail has been down, well not sure. It was down 6 times in one year. Uptime is apparently 99.8%, or down for 175 hours a decade, so 6 hours seems quite reliable. Level 3 went down last month. And in 2016. And in 2015. Having a system having to work for decades without downtime is unheard of in the web world, even in simple systems like gmail and AWS.