Who, what, why: How can an airport run out of fuel?
Manchester Airport ran out of fuel yesterday, delaying more than a dozen flights. But how does an airport run dry?
Airports are in the business of getting planes into the air. That means refuelling aircraft on the ground. So when Manchester Airport ran out of fuel this week and planes were delayed, it prompted questions about how airports receive their fuel.
Manchester gets through three million litres of aviation fuel a day. It arrives by pipeline from the Essar refinery near Ellesmere Port in Cheshire.
But a production problem meant that fuel stopped being pumped to the airport early on Wednesday morning. The 30-mile pipeline is the airport's only source of aviation fuel, every day transporting the equivalent of 79 road tankers' worth of fuel, but suddenly the flow of fuel dried up.
Usually the airport has between 12 and 24 hours of spare capacity. But the Jubilee weekend had been very busy with about 300,000 people flying over the four days, a spokesman said. And by 17:15 BST the fuel had run out.
Fuel began flowing again at the refinery at about the same time. But it takes 4-6 hours for it to travel down the 30-mile pipeline. It then needs two hours to settle as it is pumped at high pressure.
Manchester's empty tanks led to 13 flights being delayed, while 17 departures from Manchester also made a stop at other UK airports to top up fuel before completing their journey.
The incident shows up Manchester's reliance on a single source for its fuel. In contrast, Heathrow Airport has access to more than one refinery, is supplied by multiple pipelines and has access to tankers. A Heathrow spokeswoman said the airport had "days worth" of fuel in storage but refused to give an exact figure.
A bigger tank at Manchester Airport or an intermediate storage centre somewhere along the pipeline would allow the airport to store more. So why not plan for contingencies like a problem at the refinery?
Cost is the main reason. An airport wanting to store a week's worth of fuel would need to create huge storage tanks where the fuel was kept safely. And such incidents are so rare that the cost of stockpiling has to be balanced against the low probability of a shortage occurring. The vast majority of the time, the space would be totally unnecessary.
Until this incident Manchester had had no problems with getting fuel. Indeed the direct pipeline from the Essar refinery meant that during recent fuel blockades when motorists and public services were hit, the airport received an uninterrupted flow of fuel.
"The pipeline has been there since the 1960s and this is the first time that this has happened," the spokesman says.
"We've been asked why we didn't have road tankers on standby. But to have 79 road tankers on standby in case something new happens is a bit unrealistic."
David Learmount, operations and safety editor at Flight International, says the incident showed a lack of "lateral thinking" at the airport. "I've never heard of it happening before. An airport running out of fuel for aircraft is unique."
To rely purely on one source of aviation fuel is a mistake, he says. "There should be a Plan B - tankers, greater storage capacity or a second pipeline with independent pumping."
He is unconvinced by the argument that the pipeline has been operating for over 40 years with no hitch. "Manchester Airport in the 60s was like Sleepy Hollow compared to now. If they haven't advanced since then, questions need to be asked. What lateral thinking are they doing?"
There will always be a debate about what the right balance is when planning for such contingencies. But there's no getting around the fact - running out of fuel is an embarrassment an airport can do without.