I am not very familiar with the world of air traffic.

Recently I have been granted access to OpenSky Network. As I am trying to understand the "flight" dataset, I have come across a few flights that have the same departure and destination airport, what could be the reason for this?

My initial guess is that this is for maintenance purposes, and these flights have test flights done ever so often (I'm still surprised that some of these flights are performed at major international airports however).

Could this be because the data is biased?

Any help would be appreciated!

  • $\begingroup$ Try to look at FR24 or other tools: the the real path of the plane, and if it was in maintenance the days before that. Data quality check requires also to cross-check with other sources. $\endgroup$ Oct 13, 2023 at 7:26
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    $\begingroup$ What do you mean by "biased"? Can you give some examples of flights that show this? $\endgroup$ Oct 13, 2023 at 14:00
  • $\begingroup$ Bias is a term used in statistics to refer to a dataset where errors may have leaked due to mishaps in the data collection process. $\endgroup$ Oct 16, 2023 at 8:03

3 Answers 3


Many people think that almost all flight are passenger flight going from A to B, probably because this is the type of flight most people encounter in their daily lives. In reality, these types of flights are only part of a much more diverse reality.

General aviation/leisure/sightseeing flights will typically depart and arrive at the same airport, this often being the airport where the plane is parked in a hangar when not used.

For military (training) flights, an aircraft will also typically be based at a specific air base. Here you will also see flights departing, flying around in an exercise area, and then returning to the same airfield.

Same thing with civilian flight schools, where aspiring pilots learn to fly.

Then there's medical flights/HEMS/coast guard etc. Same deal.

As you speculate, there are maintainence and check flights as well, and aircraft certification flights. This is a screenshot of an 11 hour flight from Toulouse to Toulouse via the North Pole:

enter image description here


You could also have calibration flights, whose purpose it is to test and calibrate ground based navigation equipment. They will typically depart, fly various patterns around the desired navigation aids and then land again at the same airport.

Survey flights, which take the aerial photos you see on Google Maps and other services, might also depart and arrive at the same airport.

And probably many other reasons, I can't think of right now.

  • $\begingroup$ Flight tests for experimental equipment (either the aircraft itself, or something where you want to test how it performs when it's actually up in the air). $\endgroup$
    – David K
    Oct 15, 2023 at 18:30
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    $\begingroup$ Not just photographic survey flights but geophysical survey flights that use various airborne instruments to sniff out resources. $\endgroup$ Oct 16, 2023 at 0:07
  • $\begingroup$ Don't medical flights typically stop somewhere to pick up a patient? Or isn't that what you mean by medical flights? $\endgroup$
    – Llaves
    Oct 16, 2023 at 0:50
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    $\begingroup$ @Llaves There are different types of medical flights. Some might be point-to-point (e.g. a pre-arranged trip to carry a patient from one airport to another with medical personnel on board), but you could also have a medical flight that departs its home base, picks up a patient from a field or plucks them out of the ocean or off a cliffside or wherever, and returns to the base airport where a ground ambulance takes the patient the rest of the way. You could also add law enforcement flights to this list. $\endgroup$ Oct 16, 2023 at 2:23
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    $\begingroup$ Helicopters used as camera platforms for sporting / cultural events / news. Helicopters and aircraft used as aerial radio relays for television signals. For example, in road cycling, you typically have cameras on motorbikes which relay their signals to helicopters, which in turn relay their signals to airplanes, which relay them back to a ground station at the TV compound near the finish line. Especially on mountain stages where both the motorcycles and the helicopters often are deep inside valleys. $\endgroup$ Oct 16, 2023 at 16:24

Three possibilities occur to me:

  • Not so much from the giant international airports, but most student training flights and nearly all "tour" or sightseeing flights would return to their departure airport for landing.
  • Also, airlines perform plenty of maintenance work at their major hubs, so when a maintenance check flight is required, such as after certain flight control replacements or changing out both engines, those would do the same thing, returning to the same airport (and probably to be put back into service shortly thereafter, assuming the checks all passed).
  • And, rarely, you get an aircraft that departs intending to go elsewhere, encounters a problem like bad weather at its destination or a mechanical issue, and it returns to its origin. Those would both be uncommon, and unlike the other cases, the filed destination wouldn't be the same as the departure, but after the flight is over, the two would in fact be the same.
  • $\begingroup$ I can also imagine training flights start/end at the same airports. I can also imagine scientific flights doing so, although hard to imagine from a commercial airport. In the same vein, I can imagine military flights (e.g. bombing/recon flights). $\endgroup$
    – JBH
    Oct 14, 2023 at 21:04

Christchurch (New Zealand) to Christchurch via Antarctica. It's sightseeing for people who like auroras. Christchurch is the second biggest international airport in NZ.

16 page glossy e-brochure here

Astounding (high) prices).

enter image description here

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    $\begingroup$ I have no relationship with the linked website or the provider. This particular service lands at the same airport where it took off, does not land anywhere else, and accepts paying passengers. It seems to me to be a good example of what the OP was asking about. I have no intention of using the service, since I'm more interested in the destination than the journey. $\endgroup$ Oct 15, 2023 at 6:16
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    $\begingroup$ @EndAnti-SemiticHate After I had posted I remembered something about the origin of this flight, which was a response to the pandemic. What do you do with your 787s if your country has decoupled itself from the world, and you don't have enough population to fly them between cities? $\endgroup$ Oct 15, 2023 at 17:32
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    $\begingroup$ That's truly fascinating, and very innovative way to keep people employed and the aircraft running without flying them around in circles with no passengers. $\endgroup$ Oct 15, 2023 at 22:53
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    $\begingroup$ @EndAnti-SemiticHate Yes. Fly them around in big circles with passengers, and serve a nice meal with wine;-) $\endgroup$ Oct 16, 2023 at 0:13
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    $\begingroup$ @PierrePaquette NZ used to do flights over the Antarctic proper, 1977-1979. Which lead to the Flight 901 crash into Mt Erebus. A very major event in NZ society. It was said everyone in NZ knew someone who knew someone who died. Probably close to true (I did :-( ). wiki2.org/en/Mount_Erebus_disaster $\endgroup$ Oct 16, 2023 at 23:27

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