Rear-mounted “open-rotor” engines offer unrivalled environmental performance for short-haul flying due to their higher propulsive efficiency. However, there are significant difficulties in fixing such a large engine under a wing of a narrow-body aircraft, making rear-mounting of the engines the optimum solution.
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In addition to engine efficiency and weight reduction, one of the primary methods of reducing fuel burn is by reducing drag. Conventional jet aircraft currently suffer increased drag from turbulent airflow over their wings. A wing profile that allows the easyJet ecoJet to maintain laminar flow over a significant proportion of the wing will greatly reduce cruise drag.

Giving the wing a slight forward sweep increases the proportion of laminar flow over the wing (as the clean airflow from the wingtip tends to flow to the wing root in contrast to the turbulent air from the fuselage being dragged across the wing with conventional reverse sweep). In addition, it improves the stall performance of a laminar flow wing. Minimising drag is imperative in the design of glides and most gliders with laminar flow wings also have a slight forward sweep to the wing.