Her Majesty yesterday died at Balmoral in what is understood to be one of her favourite residences at the age of 96. It was soon after announced that a state funeral would follow within two weeks.
The exact date has yet to be officially confirmed.
A new document from the Department for Transport has, however, narrowed this down to at least two days.
The Department has introduced flying restrictions over Central London from 3pm today following the death of the Queen.
These will be lifted at 7am on September 19.