The influence of climate variability on transatlantic flight times

Abstract. Transatlantic aviation is a major industry and even small flight time changes have major economic and environmental implications. While our ability to optimise these flights for background wind variations at day-to-day scales is excellent, at the longer timescales needed for sustainability planning and fuel cost hedging these capabilities are more limited. Here, we quantify the association between four climate indices (the El Niño-Southern Oscillation, the North Atlantic Oscillation, the Quasi-Biennial Oscillation and solar irradiance) and transatlantic flight times using thirty years of commercial flight data. This allows us to identify whether these indices can be used to identify systematic flight time shifts. We find that ENSO and the NAO are associated with statistically-significant changes in one-way flight times of up to 82.2±3.5 minutes, and changes in round-trip times of 4.8±0.5 minutes and 4.0±0.8 minutes respectively, while the QBO and TSI have weaker but significant effects. Together, these indices plus a linear trend explain up to 27 % of variation depending on season and direction, and are associated with month-to-month fuel cost & CO2 emission variations of up to 27 MUSD & 120 kT for one-way trips and 5 million USD & 23 kT for round trips. We also show that westward, round-trip and non-winter-eastward flight times have increased by several minutes per decade since the 1990s, and that flights fly two-thirds of a standard deviation higher in altitude during solar maximum. Our results provide the first observational quantitative basis for aviation fuel and carbon cost management at monthly and longer timescales.