any reason why Thomas cook have cancelled Tunisia flights from Norwich on the Fridays which was planned to operate
do you mean why they have cut the current operating run to May 22nd - August 21st?
Big reasons for this have been a reported downturn in people wanting to travel to Tunisia following recent events etc
Also Thomson operate it from NWI on Wednesdays and also have a much bigger presence, but even they are operating for a shorter length this year, only until 24th September compared to late October last year