The ba TriStar 500s became surplus to requirements following airline restructuring. Some bright spark had realised that the RB211 installed on the TriStar burnt more fuel than the same engine on the Boeing 747. Fuel being expensive, the TriStars were up for disposal.....
....then someone else pointed out that, whilst the figures were true, the TriStar only had 3 engines, whereas the 747 had 4..
..and the burn rate was nothing like 1.3 x the 747 rate..
Ahhh......b*gger it! Too late...
