Originally Posted by
DaveReidUK
Given that it was a blurry aerial photo of an aircraft with the entire back end missing that led to the confusion, I think we can excuse the OP.
Telling the difference between a TriStar and a DC-10 from above (or below) is fairly easy as the engines on the DC-10 are closer in than those on the TriStar. This was due to the centre engine location on the DC-10 resulting in a smaller rudder area, thus requiring the engines to be closer to the centre line to meet engine out control requirements. The TriStar's bigger rudder allowed the engines to be further out on the wings, to the benefit of wing bending relief and therefore structure weight. Just one of many examples of the TriStar's more sophisticated design.