An interesting film in which the commentator suggests that B.Ae needed 350 sales to break even. Wikipedia has a lower estimate of 250 sales. I think the final total was 387 which might suggest the programme was successful. I leave it to others to debate what the choice of and number of engines did to the costs. Personally, as a former regular user of the Air UK service from Stansted to Frankfurt , I found it comfortable for the 80 minute sector and I don't think I was ever delayed more than a few minutes, even in some extreme German winter weather when the "nation's favourite airline " was cancelling some of it's flights.