This study investigated the efficacy of oral melatonin in alleviating jet lag in flight crew after a series of international flights. The optimal time for taking melatonin in this group was also investigated. In a double-blind placebo-controlled trial, 52 international cabin crew were randomly assigned to three groups; early melatonin (5 mg started 3 days prior to arrival until 5 days after return home); late melatonin (placebo for 3 days then 5 mg melatonin for 5 days); and placebo. Daily ratings showed a trend in jet lag, mood, and sleepiness measures toward an improved recovery in the late melatonin group and a worse recovery in the early melatonin group as compared to placebo. Retrospective ratings made 6 days after arrival showed the late melatonin group reported significantly less jet lag and sleep disturbance following the flight compared to placebo. The late melatonin group also showed a significantly faster recovery of energy and alertness than the early melatonin group, which reported a worse overall recovery than placebo. These findings show melatonin may have potential benefits for international aircrew.