The largest and busiest airport in Britain has warned of disruption to flights on Wednesday.
London's Heathrow Airport has said this is to "ensure silence" as Queen Elizabeth II's coffin is brought through the British capital.
The airport said this was "out of respect for the period of mourning".
It said some flights between 1.50pm and 3.40pm on Wednesday will be "disrupted to ensure silence during the ceremonial procession."
It added that airlines will notify passengers directly of any flight changes.
Out of respect for the period of mourning following the passing of Her Majesty The Queen, some flights between 13:50–15:40 on Wed 14 Sept will be disrupted to ensure silence during the ceremonial procession.
Airlines will notify passengers directly of any flight changes. (1/3)
— Heathrow Airport (@HeathrowAirport) September 13, 2022
Heathrow operators have also said there would be further disruption next Monday during the actual funeral.
"We anticipate further changes to the Heathrow operation on Mon 19 Sept, when her majesty's funeral is due to take place.
"We apologise for the disruption caused, as we work to limit the impact on the upcoming events", it said.
Mourning in the UK for the former monarch has been likened to old traditions seen in the former Soviet Union by Newstalk Breakfast host Shane Coleman.
He said: "There are echoes of the former Soviet Union, and the passing of a general-secretary of the Communist Party, about the extent of the coverage.
"I do think some of it is a little bit over the top.
"I heard a presenter on television yesterday, saying he steeled himself for the whole weekend so he wouldn't get upset on television - and then he thought of the queen and how stoic she would be.
"Let's call it out as it is: there's some pretty bonkers stuff going on."