Southwest Airlines' competitive advantage came entirely from one unusual operational decision

For most of its history, Southwest Airlines operated only Boeing 737 aircraft — every single plane in its fleet. This seemingly trivial decision had enormous cascading benefits: mechanics needed training on one aircraft type only; spare parts were interchangeable across the fleet; pilots could fly any route without requalification; and gate turnaround times shrank to 25 minutes because processes were standardised. Southwest's fleet homogeneity is a textbook example of operational excellence — a constraint that looks like a limitation but becomes the source of competitive advantage.

Source: Pfeffer, J. & Sutton, R.I., The Knowing-Doing Gap (Harvard Business School Press, 2000)