There is no apparently about it. All take off performance is based on the loss of an engine at V1. Aircraft have to be able to carry on the take off with only one engine operative. The close nature of the hills at ACE mean that take off weights are restrictive when departing runway 03. Some times tech stops are simply unavoidable give an aircrafts capabilities. It is certainly not unique to Jet2. The ACE-BLK schedule caters for a tech stop, if needed, so far the flights have performed very well and re-fuel stops are few and far between.