Air travel has increased steadily over the last decade, and its effect on the health of passengers has been the subject of much debate. There is a paucity of evidence on the effects of air travel on oxygen saturation in general populations. The peripheral oxygen saturation and pulse rate of 84 passengers, aged 1–78 years, were measured by pulse oximetry at round level and altitude during air travel. There was a statistically significant reduction in oxygen saturation in all passengers travelling long haul and short haul flights (p < 0.05). The mean [range] (SD) SpO2 for all flights at ground level was 97% [93–100] (1.33) and at cruising altitude 93% [85–98] (2.33). Fifty-four per cent of passengers had SpO2 values of 94% or less at cruising altitude. This is a value which may prompt physicians to administer supplemental oxygen in hospital patients.