Why is it that whenever we have even just a hint of bad weather, our airports seem to go into meltdown?
With freezing fog engulfing the capital on Monday January 23, Heathrow Airport cancelled around 100 flights, advising passengers to check the status of their flight before travelling to the airport.
But why is there a need to cancel flights entirely and why does the weather pose such a serious problem to the UK's busiest airport?
Why does fog cause delays?
Similarly to the way fog affects motorists, pilots experience reduced visibility, meaning more space must be left between them and the plane in front.
Creating more space then has knock-on effects as not as many planes are able to take-off or land each hour, meaning delays or cancellations to flights.
What distance should planes be spaced from each other?
Arriving aircraft are generally spaced around three miles apart, with that increasing to six miles in poor visibility.
However, it does depend on the size of the aircraft, due to the vortex left in the air, larger planes require a bigger gap than smaller planes.
Why can't Heathrow Airport cope with poor weather conditions?
Heathrow operates at 98% capacity, with a plane landing or taking off every 45 seconds.
When the airport experiences fog, snow or other problematic weather conditions, it has to space out flights which inevitably causes delays and cancellations as there is no space to accommodate delayed flights.
Why can't technology help?
Yes, planes are fitted with technology that enables them to fly through fog, it is the safety on the ground which causes the issues.
In low visibility protocols (LVPs) the preceding aircraft must land and clear the runway before clearance is giving for the following aircraft to land.
When LVPs are applied at Heathrow, the spacing on approach is increased from three to six miles.
When on the ground, as visibility will also be poor, extra time and space has to be allowed when manoeuvring aircraft and other items.
The ground teams may need to remove snow and ice from the runways and taxiways, this all plays a part in the reason for spacing out incoming planes.
Why do airports cancel flights in advance?
Cancelling flights in advance is a measure taken by the airport to aim to reduce disruption for passengers.
It helps to avoid flights being cancelled at short notice, leaving passengers stranded in the terminal.
It also allows airlines to re-book passengers on other flights which have space.
Who makes the decision to cancel flights?
When severe disruptions are expected at Heathrow Airport, such as freezing fog, a decision is made in advance to potentially cancel flights.
The decision is made by Heathrow Airport, National Air Traffic Services (NATS) and the individual airlines.
Once a decision is made to reduce the schedule, the airlines then decide which of their flights to cancel.
Passengers are warned to check their flight status before travelling to the airport.
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