**Both airlines are trying to serve the same desirable travel window.** Spreading departures evenly throughout the day might look sensible, but passenger demand—and the connections that feed each flight—isn’t evenly spread.

For your Los Angeles–Melbourne example, a late-evening departure has several advantages:

- Passengers can reach LAX on connecting flights from across North America during the day.
- The roughly 16-hour journey brings them into Melbourne in the morning, leaving a useful day ahead and opportunities for onward connections.
- Passengers can start the journey with dinner and sleep.

Published schedules show both UA98 and QF94 using that evening-departure/morning-arrival pattern, though the exact times vary by season and date. These are likely scheduling advantages; they aren’t confirmation of either airline’s specific planning decisions. [LAX–Melbourne schedules](https://www.wego.com/schedules/lax/mel/flight-schedules-from-los-angeles-4008-to-melbourne-4534)

The same principle applies to regional flights: business passengers often want to arrive before work or leave after it. At connecting hubs, airlines also group arrivals and departures into waves, so passengers can transfer between many different routes. United explicitly describes how arranging these “banks” increases connection opportunities. [United investor presentation](https://ir.united.com/static-files/567c302e-0e09-47c5-814f-f1f30d732129)

**Competition itself encourages clustering.** If most customers want an 8 a.m. flight, an airline offering noon doesn’t automatically capture an underserved market—it may simply lose customers to the competitor offering 8 a.m. Each airline also draws passengers from its own connecting network, loyalty program and corporate contracts.

And neither aircraft needs to be full every time. Profitability depends on fares, operating costs, cargo revenue and the value of connecting journeys, not just the percentage of seats occupied. Moving a partly full flight to an unpopular time could make it emptier still.

Airport slots, curfews and aircraft rotations can narrow the choices further, although Melbourne itself operates without a curfew. [Melbourne Airport operations manual](https://www.melbourneairport.com.au/_assets/be08d7b0-97a1-02f9-2be6-a0c139c3c337/4d4dec68-293d-4ee8-b4ad-534de2e05384/MA0162_Terminal_Operations_Manual_Retailers%20V6.pdf)

The apparent “formation” is a separate consequence: flights with similar departure times, speeds and wind-efficient routes can remain near one another on a tracking map for hours, while air traffic control maintains separation.