Aircraft emissions impact human health though degradation of air quality. The majority of previous analyses of air quality impacts from aviation have considered only landing and takeoff emissions. We show that aircraft cruise emissions impact human health over a hemispheric scale and provide the first estimate of premature mortalities attributable to aircraft emissions globally. We estimate 8000 premature mortalities per year are attributable to aircraft cruise emissions. This represents 80% of the total impact of aviation (where the total includes the effects of landing and takeoff emissions), and 1% of air quality-related premature mortalities from all sources. However, we note that the impact of landing and takeoff emissions is likely to be under-resolved. Secondary H2SO4?HNO3?NH3 aerosols are found to dominate mortality impacts.