I've noticed that many times 2 or sometimes more airlines will have aircraft departing the same airport within minutes of each other heading for the same destination. For example at this moment UAL 98 and QF 94 departed LAX at roughly the same time heading for Melbourne Australia. As I type they are flying almost in formation over New Caledonia. I see this again and again from regional flights to trans ocean flights. I can't imagine that both flights are full every time. What is the rationale for competing airlines to fly at the same time and arrive at the same time?
In addition to the practical considerations noted in the other answers, there's also the fact that the internal logic of competition (Hotelling's Law, as helpfully pointed out by AE) is an incentive for each airline to schedule their flight at the same time as the competing flight.
Suppose there are a certain number of people who need to go from PPP to QQQ. Each traveler has an ideal time they would like to fly, and will buy a ticket from the airline that comes closest to that.
Now if airline A has a departure at 10:00 and airline B has a departure at 12:00, airline A can improve its market share by moving its departure to 11:00 -- namely, the passengers with a preferred departure time between 11:00 and 11:30 will then switch from B to A, and everyone else stays with the same airline. Those who prefer to go before 11:00 flew with A before and still do; those who prefer to go after 11:30 flew with B before and still do.
After some maneuvering of this kind, airlines A and B will end up having both their departures scheduled right next to each other around the median of the customers' preferences, sharing the market about equally. In this situation neither airline will have anything to gain by moving their departure -- on the contrary, that would leave them as the best-fitting choice for less than half of the market, which would lose business.
(In the real world, there are other considerations of course, such as the availability of connections if A and B have hubs at different ends of the route, crew and aircraft scheduling constraints and so forth -- so it doesn't always end up this way).
There are actually quite a number of restrictions on flight timing:
- Airport noise regulations. Aircraft can't depart or arrive too late or too early in the day. When you take into account the restrictions in 2 airports, and add the flight time uncertainty of a long trans-oceanic flight, you may not have many time options left.
- Airport opening hours (many airports, especially smaller ones, are not open 24 hours a day)
- Passenger preferences. First, there's obvious preferences (like not departing/arriving in the middle of the night). Then there may be less obvious forces that shape demand, like the preferences of business travelers (typical business meeting schedules, etc). All this means that there may be a demand peak at a certain time, and any airline that deviates from that peak would lose out.
- Airline internal optimization. On the one hand, the airline wants to utilize the aircraft as much as possible - the plane is not making any money if it's sitting idle. On the other hand, there are minimum crew rest times (including union rules) and minimal maintenance windows. These factors are similar from airline to airline. When you take all these factors into account it may not leave much choice of times if you want to have an optimized schedule (especially if you want to have some regularity in the schedule).
- Schedule of connections in the departure/arrival airports
I'm going to basically add an extended comment to Henning's answer, who is spot-on.
Primer in Economics: Hotelling's Law
Avoiding product-differentiation can sometimes be optimal and is a very well-known phenomenon within Economics. It is more formally known as Hotelling's Law.
I'm going to introduce it here in the standard simplified environment, lemonade sellers at a beach.
Imagine a horizontal beach (on a straight line), where customers are evenly-spaced.
Now there is two lemonade sellers, both indicated by x and y. The
| indicates the center-point between the sellers. Every customer will go to the lemonade stand that is closer to him:
All the customers left to the center will go to
x, the others to
y. Note that if
y goes closer to
x, he will shift the center-point to the left, meaning that he will attract more customers.
Yes, he is further away to some of his customers (the ones on the right end, but these have no alternative, so they will stick with them.
x will respond to movements of
y and vice-versa. The only stable solution is where both are "exactly on top of each other", and share the customers evenly.
Back to Airplanes
Now, whether we observe this market phenomenon in reality depends on what I highlighted, that the customers have no alternative. So you should see this phenomenon happening more so on schedules with less competition.
Observe that we can also interpret the real line as time, and
y as two scheduled flights at different times. One can translate the intuition one-to-one and will get to Henning's answer.
Is this a relevant mechanism?
Hotelling's rule finds application in many different settings, for example
- distribution of political parties (on different topics)
- large branded chains (having similar goods in terms of quality and prices)
The linked wikipedia page actually mentions the flight-schedule of Jet Blue as an example.
I'll take a stab at this.
In the past, I've observed this as well, and I am sure that, at least sometimes, these are not codeshared flights.
On routes where many connections are available, this will come down to coincidence, but it can seem baffling when, say, the only two daily connections between two cities leave minutes apart, like in the example OP provides.
However, for all the examples that I remember observing, this was a consequence of the the two cities being best served at the times the flights connected them.
Specifically, in OP's example, UAL 98 leaves at around 10:30pm, and is set to arrive around 9:30am. QF 94 is set to depart at around 10:15pm, arriving around 9am. Obviously, by leaving at the end of the day, and arriving at the start of another day, the time 'lost' by passengers is minimised: if one of these flights would leave in the morning and arrive at night, the nights before and after, as well as the day spent in transit, would all be 'lost'. Now, the daytime lost in transit is minimised.
(Added:) Furthermore, if flights are relatively infrequent, a competing airline will know there's a market for a certain connection at a certain time, if a connection already exists. It then is easiest to simply offer the exact same flight as opposed to test the waters with a completely different departure and arrival time.
This is exactly the same reasoning that leads to medeaval cities having streets dedicated to one type of shop ('baker street', 'butcher street', etc.)
This is primarily a function of time zones and operational efficiency on the airline. Ideally international flights depart and arrive so that they can accommodate incoming and continuing connections from smaller local & connection flights. Obviously you also want to avoid the middle of the night in either time zone.
For example New York -> Frankfurt is served by Lufthansa, Singapore, Delta & United. The viable departure window for transatlantic flights from the east coast starts mid-late afternoon (super early arrival in Europe) to late night departure (airports shutting down in the US). Lufthansa actually captures the full window with three different flights at 4pm, 6m, and 10 pm. The other three carriers have a single daily flight almost at the exact same time (8pm). Lufthansa has a huge hub in FRA with lost of connecting flights during all of the day and for the US carriers 8pm is late enough to bring in most domestic connections.
Further to the already submitted answers, there is another reason why this may occur - the legal aspect, or collusion.
It is against the law for two companies to work together in order to reduce competition between the two. If Airline A was to speak to Airline B, and say "hey, you guys keep operating your 10am flight, and we'll move our flight to 2pm", then they would be falling fowl of competition laws.
A "joint venture" needs to be signed and agreed on by the relevant government authorities before two airlines can co-ordinate pricing and scheduling of flights.
The main reason are probably the connections. Flights may have relevant connections that depart only at certain times at a day.
Especially when searching for a flight time that both matches with many connections before and with many connections after the flight, it is no wonder that options are limited and different airlines arrive at essentially the same timings.
Interesting question, and after reading all the answer, I noticed most forgot that the time and frequencies are actually dictate by computer.
What most airlines have in common? TICKETING SYSTEM!
Not only it is made for ticket booking, but also meant to calculate the cost and profit for a single journey, airplane optimisation, and also FLYING TIME based on input parameters (airport curfew, ground handling, catering, refuel frequencies, flying hours and on top of that MARKET RESEARCH which includes time preference, market demand, school holiday, etc).
Most but not all airlines are using A***LO (cant specifically named it, sorry) which is maintained by indian staff in Pune, India. So, doesnt matter which airlines is calculating or projecting one year flying schedule, they are normally come out almost similar as same parameters were fed in!
No single airline can cope with market research as it is global, hence most turn to a number of research house, YouGov, etc.
But, it is not final yet. You have to submit your planned timetable to the airport authority along with route taken to be fit in into their model, small airport maybe OK, but Heathrow with gaps of 45 seconds to the next landing plane? Or those in Australia with night-curfew? When these operators put into their patterns, then it will calculate again whether it fits with airport requirement and normally come out with minor adjustment - and these system dont discriminate airlines, they only recognise route, code, stack, estimated time and estimated fuel balance requirement.
Whilst the brand of the airlines maybe different and they are heading to the same place at almost the same time, but their planning system were all made and maintained by one company.
Sometimes there are agreements between governments allowing each other airlines to fly between their state controlled air ports. These agreements must be fair, so both state owned airline can fly at the best times, therefore often both flight at the same time.
Even when the states have let go of some of the control, by then the “slots” at the airports are mostly taken up, so it is hard to change flight times.