AI mesh question

[LootMoar]

Hey all - I've been messing around with creating my own custom towns etc, but the one thing I can't figure out is how to delete a section of the ai mesh!

It's driving me crazy

Any help would be very much appreciated, thank you

Edit: Discovered the answer - because I am on a mac I needed to press the 'fn' key in conjunction with the backspace key, since I guess Windows treats backspace and delete as different keys.