1. Minimum-time route location is linked to the jet stream Eastbound: New York - London fly in the jet stream Westbound: London - New York avoid the jet stream 1 Irvine et al., 2013, Meteorological Applications

2. Winter weather types are characterised by the jet stream Eastbound Westbound Irvine et al., 2013, Met. Apps. 2 W1. strong zonal jet W2. Strong tilted jet W4. Confined jet Pressure pattern at flight level (black) and jet stream (red). Daily minimum-time routes between London and New York (blue).

3. FL300FL340FL390 W1. Zonal jet W2. Tilted jet W4. Confined jet Eastbound routes Westbound routes tropopause Contrail formation regions are linked to the weather pattern

4. Route time varies according to the weather pattern

5. Jet stream location is related to the North Atlantic Oscillation 5 Diagrams from: http://www.ldeo.columbia.edu/res/pi/NAO/ Positive NAO jet stream further north Negative NAO jet stream further south

6. Frequency of winter weather patterns TypeJet streamFrequency PositionStrength(days/season) W1zonalstrong17 W2tiltedstrong17 W3tiltedweak15 W4confinedstrong15 W5confinedweak26 6