At least Jet2 actually try to get all their flights off when they can, compared to other airlines who seem happy to chop a few out, thouh i do suspect a few of those, would be due to capacity on route.
I do get why Jet2 have their planes full early to take advantage of earlier Slots when possible, but this can backfire if it isn't possible. A friend was coming back from PMI and was on the plane for 2 hours before they were allowed to takeoff. Not the most comfortable place to be couped up, but it could have be worse.