OBJECTIVE Jet lag is common place amongst long-haul cabin crew. Timed food has been shown to reset the circadian rhythm in rodents. Implementation intentions have been used to change eating behaviour. Mealtimes could therefore be used as a countermeasure to reduce jet lag and improve alertness in long-haul cabin crew through forming an implementation intention to improve the regularity of meals on days off. DESIGN Sixty long-haul crew took part in a randomised controlled trial, with two conditions: forming an implementation intention to eat regular meals on days off vs. no implementation intention. Pre-intervention measurements were taken at baseline (before a long-haul trip) and post-intervention measures were taken on the first and second days off post-trip. MAIN OUTCOME MEASURES Subjective jet lag (unidimensional and multidimensional) and objective alertness (Psychomotor Vigilance Task (PVT)). RESULTS Mixed ANOVA showed a significant condition x time interaction for unidimensional jet lag but not for multidimensional jet lag and objective alertness. In particular, the formation of an implementation intention to alter mealtimes resulted in a reduction of unidimensional jet lag. CONCLUSION Implementation intentions can be used to alleviate jet lag in long-haul crew through promoting a change in mealtimes.