The lowest fares on a route often attach to a departure before dawn or close to midnight. The pattern is a direct consequence of how airlines use aircraft across a day.

Aircraft earn nothing on the ground

An aircraft represents a large fixed cost that accrues whether it flies or parks. The way to spread that cost is to fly more sectors between the first departure and the last arrival.

Schedules are therefore built to extend the operating day at both ends, which means a first flight leaving very early and a last one arriving very late.

Those two sectors exist to position the aircraft for the profitable middle of the day as much as to carry their own passengers.

The marginal seat is nearly free

Once a flight is scheduled, crewed and fueled, the additional cost of carrying one more passenger is small. It is essentially the weight of the person and their bag.

Any fare above that marginal cost contributes something toward the fixed costs already committed. An empty seat contributes nothing.

Airlines will therefore price the unpopular hours down aggressively rather than fly with rows empty.

Demand at those hours is genuinely thin

Most travelers will pay to avoid a three in the morning alarm or an arrival after public transport has stopped. The willingness to pay is lower, and pricing follows it.

This creates a stable arrangement where price-sensitive passengers self-select into the inconvenient departures and time-sensitive ones pay for the middle of the day.

The savings are partly transferred, not created

A very early departure often requires a night near the airport, an expensive ground transfer or a lost working day at the other end.

Those costs sit outside the fare, so the ticket looks cheaper than the trip actually is. The comparison worth making is total cost from door to door.

For a traveler already staying near the airport, the discount is real; for one traveling from an outer suburb, much of it evaporates.

Reliability differs across the day

The first departure of the morning usually operates with an aircraft that spent the night at the airport, so it starts the day without inherited delay.

Late evening departures sit at the end of a long chain and absorb everything that went wrong earlier, which makes them the least punctual part of the schedule.

The same low fare therefore buys very different reliability depending on which end of the day it sits at.