Delaware only has 3 counties......those towers are in Sussex...................Kent is in the north.....where the Dupont family is from..

The Da Vinci Code (2006) - Filming & Production - IMDb

https://www.imdb.com/title/tt0382625/locations

The Da Vinci Code (2006) Movies, TV, Celebs, and more... ... No. Biggin Hill Airport, Biggin Hill, Kent, England, UK · 5 of 5 found this interesting Interesting? Yes

The Da Vinci Code Chapter 81 Summary - Shmoop

https://www.shmoop.com/the-da-vinci-code/chapter-81-summary.html

The Executive Services Officer at Biggin Hill Airport, Simon Edwards, is not pleased that the French are forcing him to help arrest one of his most lucrative clients.