In 1968 a Hawker Siddeley Trident was certificated to fly a category II autoland, permitting landing in fog with some forward visibility. By 1975 it had been cleared for category IIIB, which means it could land completely blind, and the exercise was only limited by the fact that the pilot needed sufficient visibility to taxi the aircraft off the runway and find the stand.
British Airways at Heathrow was the first regular user of Cat IIIB autoland.
Today at Heathrow there was Cat II fog, and my BA flight to Stockholm was cancelled along with lots of others. It was not for lack of technical capability, just because Heathrow’s schedules depend on good weather. If the weather is anything other than good (particularly visibility and wind), cancellations result because there is no slack in the system to allow for delays. The delays are inevitable in fog because, for safety, aircraft on approach have to be spaced further apart when the pilots cannot see the aircraft ahead, and the same for departures. And taxiing on the ground is slower.
Because Britain is affected by this thing called weather (allegedly), its airports would normally be expected to take weather into account in planning their schedules. But they don’t because demand for air travel is higher than the infrastructure can provide in all but perfect weather. So they plan for perfect weather and cancel flights the rest of the time.
This is particularly true at Heathrow, where there is no slack at all.
The message to air travellers is don’t plan to interline at Heathrow, and if you’re a multinational looking at London as a possible new site, go elsewhere because London doesn’t have reliable connectivity.
Back in the 1960s when Britain was developing a system to permit aircraft to operate safely in fog, successive governments were considering the options for new runway capacity for the south-east of England. They considered it, then cancelled it – and have repeated that exercise multiple times since then. That’s why my flight has been cancelled.