A red eye flight is a flight that takes off late at night and arrives early in the morning, usually taking off after 9 p.m. and arriving by 5 or 6 a.m. So, in taking a night flight, you’ll be in the sky overnight, when you would typically be asleep. Typically, these flights travel west to east (i.e. Los Angeles to New York, Los Angeles to Toronto, or Vancouver to Toronto), so travelers arrive in an earlier time zone with a full day in their place, rather than arriving somewhere midday or in the evening and losing a whole day to sky travel.