A Multi-stage Centralized Approach to Formation Flight Routing and Assignment of Long-haul Airline Operations

Abstract

This paper describes the development of an optimization-based multi-stage centralized planning system for the efficient routing and assignment of extended flight formations in commercial airline operations. In an extended formation, where aircraft are longitudinally separated by 5-40 wingspans, a trailing aircraft can attain a reduction in induced drag at fixed lift, and consequently in fuel burn, by flying in the upwash of the leading aircraft’s wake. To organize the assembly of flight formations on a network-wide scale essentially two distinct approaches can be taken, viz., a centralized approach and a decentralized approach. Both approaches have distinct advantages and disadvantages. In this study a novel multi-stage method for flight formation assignment is proposed that combines the advantages of the decentralized approach (fast computation and reduced vulnerability to flight delays) with the main benefit of the centralized approach (a near-global optimum in terms of fuel savings). The multi-stage centralized approach that we propose is validated and subsequently demonstrated in a case study involving a wave of 267 eastbound transatlantic flights. In the case study fuel savings of 6.8% are recorded (relative to flying “solo”), while flying in formations comprising up to 16 aircraft.