Amazon this week blamed a power outage and a resulting generator failure for a Web services blackout that took down Internet firms like Instagram and Netflix on Friday night.

"We apologise for the inconvenience and trouble this caused for affected customers," Amazon said in a note on its AWS website. "We will spend many hours over the coming days and weeks improving our understanding of the details of the various parts of this event and determining how to make further changes to improve our services and processes."

Electrical storms that blasted the East Coast of America on Friday night pulled the plug on some of Amazon's servers in Northern Virginia, leading to issues with what Amazon refers to as its Elastic Compute Cloud, Relational Database Service (RDS), and Elastic Beanstalk.

Amazon said this week that a generator failure at one of its multiple data centres resulted in the outage.

The trouble started with a voltage strike in electrical switching equipment at two data centres. In one of those centres the generator worked fine, but it failed to provide stable voltage in the other. 

Amazon said that its equipment had all worked fine and tested well prior to Friday's failure. But given last week's troubles, the company pledged to "lengthen the amount of time the electrical switching equipment gives the generators to reach stable power before the switch board assesses whether the generators are ready to accept the full power load."

"Additionally, we will expand the power quality tolerances allowed when evaluating whether to switch the load to generator power," Amazon said.

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