A massive IT glitch has crashed computer systems around the world. Airports, hospitals and businesses have been affected, with computers shut down or unable to access networks. The main reason is an outage in Microsoft's cloud services and related apps. Travel disruptions have been the most obvious consequence of the global IT failure. Airports stretching from the US to Australia and including India, the UAE, Hong Kong, Singapore and Malaysia all saw their booking systems fail, forcing staff to check in passengers manually.