The projected increase in the demand for commercial air travel advocates for energy-efficient airplanes and reduced carbon footprint. In the past, airlines mostly relied on the infamous hub-and-spoke model for their long-haul operations.

In recent times though, more airlines are moving towards point-to-point travel — connecting relatively smaller city pairs through short-haul flights. The trend calls for specific economic viability for the airline in terms of fuel efficiency, carbon footprint, and aircraft maintenance.

Aerodynamic drag

Fuel efficiency is directly affected by the magnitudes of drag airliners experience during flight. Apart from the parasite drag (form, interference, and skin friction), a large portion of the aerodynamic drag results from the airflow rolling from the higher-pressure side of the wing to the lower-pressure side, causing wingtip vortices.

Lift-induced drag is generated as a byproduct of the downwash from the vortices, which affects the aerodynamic efficiency of the aircraft. Depending upon the aircraft type and phase of flight, approximately 35 to 40 % of the total drag can be associated with lift-induced drag.

Since the strength of vortices is directly proportional to the angle of attack, the overall economics of flight changes significantly between various flight regimes.

Fuel efficiency

In a typical long-haul flight, an aircraft climbs (to cruising…