If you work in technology there’s often a joke about someone tripping over the power cord whenever a server goes down. It appears that joke became reality for British Airways last weekend. British Airways flights were disrupted worldwide due to a power supply issue in the company’s main datacenter, with 75,000 passengers affected by canceled flights. The Times reports that the datacenter shutdown was triggered by a contractor accidentally switching off the power supply.

British Airways was forced to cancel all flights from Heathrow and Gatwick in London over a popular public holiday weekend, as all of the company’s IT systems were affected. An investigation will now take place, but will likely focus on human error rather than equipment failure. British Airways will also have to answer why the company wasn’t better prepared for power supply issues, especially after being accused of cost-cutting and outsourcing IT jobs. The Guardian reports that British Airways now faces a compensation bill of more than £100 million ($128 million) for the chaos caused by the power supply problems.