As far as I am aware Heathrow holds a committee to discuss bad weather events and if they decide to reduce capacity then airlines must reduce services. From what I gather, domestic services are culled first to protect long haul operations but I think this particular decision is taken by the airlines.
There's no way Heathrow would want another day like this...
Yes so in the case of predicted weather which impacts arrivals rates, if there is bad weather forecast NATS provide to HAL a landing rate prediction for the following day broken down by hour. Obviously if that prediction is less than the scheduled demand some action needs to be taken.
My understanding as explained by a friend at LHR who is a senior NATS controller is there are two possible processes:
1. A process called 'HADACAB' - airlines have signed up to this and HAL can force a specified percentage reduction of the schedule across the board. The specific flights to be cancelled is left up to the airlines.
2. There is a non-mandatory process called Demand v Capacity where HAL and NATS inform all the airlines that if nothing is cancelled there will be y delays and a reduction of x% is recommended.
The above is what kicks in usually when there are storms resulting in high winds. To some extent for winds which are mostly headwinds the use of
TBS mitigates the reduction in arrival rates, although TBS is not much use if the wind is mostly crosswind. What happens usually is BA and other airlines will plan to cancel some flights. With BA they load the cancellations in at around 4pm on the day before the disrupted day.
However, this is
not what has happened today. HAL and NATS have not demanded or asked for a reduction. The snowfall has been at a level where HAL has been able to cope with clearing the areas they are responsible for - so maneuvering areas, taxiways, runways. and NATS has been able to maintain the required arrival rate. After 2010 which that video shows HAL invested a lot of money in new snow clearing equipment to ensure they had more capacity to clear snow.
At LHR each airline is responsible for de-icing their own aircraft. BA do their aircraft themselves using their own people and equipment, other airlines use the usual handling agents.
What has happened today is that BA has decided themselves to reduce their own schedule. BA simply do not have enough people and equipment to de-ice their aircraft fast enough to maintain their full program. You may remember back on 10 December when snow fell and BA did try to maintain the full schedule in the face of some snow which wasn't predicted and the whole day's operation rapidly fell apart since aircraft were constantly waiting to be de-iced thereby blocking stands which then prevented the landing aircraft from using them.
In order to avoid that happening again. BA have decided what level of operation they can run and manage to de-ice and then reduced flights to match that. Typically reductions are targeted at short haul & domestic and those routes with multiple rotations in order to allow some re-booking. BA decided yesterday what they thought they could operate, and what they wanted to cancel and loaded them in to the system around 4pm on Sunday - all the texts and emails notifying customers of cancellations today went out yesterday. BA have just repeated this process today so cancellations for tomorrow were loaded in around 4pm and texts & emails went out to customers on tomorrow's affected flights.
