Regarding stopping flights, the reason given was for silence. Specifically they are stopping Heathrow flights. They are not stopping flights from other London’s airports (nor other European airports.)
[There will be no aircraft movement for 30 minutes around noon on Monday to ensure skies over London remain quiet during the two-minute silence at the end of the funeral, Heathrow said.
"Operations to and from the airport will be subject to appropriate changes in order to avoid noise disruption at certain locations at specific times on Monday," a Heathrow spokesperson said in a statement.]
With regards to Jacqui, I saw an article about some random woman in Australia that was selected to attend the funeral - she was one of 10 “everyday” Australians invited. So, it’s not all famous dignitaries who are going. So, I guess I don’t know if she will be sitting in the cheap seats or standing outside, especially if she used the word “go” vs “invited” (although “invited” may sound a bit pretentious and she’s not like that.)