Singapore Airlines was the first airline to introduce ultra-long range (ULR) flights, flights longer than 16 hours in duration, between Singapore (SIN) and Los Angeles (LAX). These ULR flights present a challenge for airlines and regulators, as they can potentially increase fatigue-related operational risk, particularly during the later stages of the flight, if they lead to restricted sleep and extended periods of wakefulness. Providing crewmembers with scheduled in-flight rest breaks for sleep in crew rest facilities is the main fatigue mitigation strategy in ULR operations.

To assess the effectiveness of this strategy, in-flight sleep of 41 flight crew (with 6 crew members participating on two occasions) was recorded using polysomnography (PSG), and crew members completed a 10-min psychomotor vigilance task (PVT) at key times during each flight. Sleep patterns were also monitored with actigraphy and sleep diaries from 3 days pre-trip, throughout the out-and-back trip, which included a 2- or 3-day layover, and for 3 days post-trip.