Flights and fog

[Pharlap]

Excuse my ignorance, but I do not understand why the flights and ferrys are cancelled due to poor visibility. What do they do at night. I understood that aircraft computers virtually take off and land the planes themselves as for ferrys the sea at night is as black as you can get

[delboy3]

It puzzles me, too, what with all the advances in ground radar - however, bear in mind that there have been some horrific accidents in fog, most recently at Milan Airport in 2001. Better safe than sorry perhaps?

[SteveD]

I think that it also involves safety regarding airport ground vehicles. They are reducing the number of aircraft movements.

Also, of course, if a flight from Heathrow to Glasgow is cancelled because of the fog, then the return flight from Glasgow to Heathrow will also be cancelled and there will also be a knock-on effect because the aircraft is unavailable.

One thing is certain, however, and that is that the last thing airlines and airports want to do is cancel flights; airlines because of lost passenger revenue and airports because of lost fees from the airlines.

[heathfield]

When aircraft land at night the pilots use the runway and taxiway lights to guide them. They can't do that if it's foggy.
The automatic landing system's ground equipment needs a clear line of sight to the aircraft it's guiding. On a normal day, planes are stacked one behind the other, and they block the auto system of the plane behind them. Instead, they have to reduce the number of planes approaching the airport to allow this clear line of sight. Flights have to be cancelled to permit this increased spacing between planes on approach.
Ferries too use lights at night to guide them. And they have the advantage of being able to stop if they need to. (Unlike planes!). Radar is used for navigation, but if it's really foggy and they can't see the dockside when arriving or leaving, then it's deemed to be unsafe, and they won't sail.

[buildersmate]

It's incredibly simple. The distance between planes landing is planned to be 3 miles. Because of the what Heathfield (correctly) says, the distance has to increase to 5 miles. Outcome - fewer landing slots. Result - fewer planes landing, unless more planes are allowed to land at night. Since LHR is loaded to virtually 100% capacity, there's a knock-on effect.
The prat of a reporter that interviewed both a Finnish national and a couple of Americans who whinged the Brits didn't know who to run the service did us a complete dis-service. US airports just aren't loaded to the same level of capacity, and planes land at Helsinki once in a blue moon.

[rosojoly]

check heathfields answer and buildersmate both right