You're probably asking yourself how an airport could run out of something like that. Well, it's lot more simple than the process of refueling the darn thing. 

"It is the first time that the airport – the UK's third busiest in terms of passenger numbers – has run out of fuel in its long history," writes The Guardian's Helen Carter, who adds that this blip could cause massive delays and mass cancellations. The Telegraph's David Millward notes that up to 150 flights could be canceled today. 

The whole thing is supposed to go down in around an hour--6 p.m. London time, and officials believe the cause has to do with "quality concerns" at the Stanlow oil refinery, which pumps 250,000 liters an hour to the airport. "The airport hopes the problem will be resolved by midnight on Wednesday but the knock-on effect on services will continue until Thursday, as it takes eight hours to pump a day's supply of fuel," The Guardian's Carter writes. Apparently the airport relies on that pipeline and why trucks just won't do the trick. Per Carter: 

Manchester airport uses 3m litres of fuel a day. A standard tanker can only carry 38,000 litres. The airport had looked at alternative sources of fuel, but was unable to identify one. It would require 79 trucks to provide enough fuel for 24 hours' supply.