The outage underscored a central trade-off of cloud computing: while it lets businesses deploy global services without maintaining vast infrastructure, it concentrates risk. A problem in a single region—like Northern Virginia—can cause widespread, simultaneous outages for unrelated companies worldwide.

A United system outage caused by the AWS crash also reportedly caused long lines and disrupted check-ins and bag drop-offs across airports in the United States, according to the airline’s own X posts in response to customer complaints. The outage is yet to lead to massive delays, but Delta reported facing some minor ones.

Since a large portion of the internet depends on AWS, the outage cascaded across major firms in disparate industries, leaving some people unable to access airline information or make everyday purchases, Qi Liao, a professor of computer science at Central Michigan University, told ABC News.

Amazon’s cloud computer service is recovering from a major outage that disrupted online activity around the world for several hours on Monday.