OpenSky Network explained: open flight data for spotters and research

You’re standing at the fence, an unfamiliar aircraft turns onto final, and you see it on your phone on one of the big flight trackers. What many spotters don’t know: besides Flightradar24, FlightAware and the like, there is a network that has been collecting the same signals for over a decade but pursues a completely different purpose. The OpenSky Network is a nonprofit research consortium with a huge data archive. This article explains how OpenSky works, what the live map and the REST API offer spotters, who can access the historical data and why you get a better quota as a feeder.

OpenSky Network: the short answer

The OpenSky Network is a nonprofit association under Swiss law based in Burgdorf. It operates a worldwide network of receivers that pick up signals from aircraft transponders and stores this raw data in a large historical database. The receivers are hosted by volunteers, companies, universities and authorities. Who gets the data depends on the purpose: research gets full access, individuals use the live map, a REST API with a daily quota and publicly available datasets. Commercial users need a license.

That makes OpenSky fundamentally different from the flight trackers you probably know from the flight tracker app comparison. There, the emphasis is on a fast, nicely presented live view with schedules and photos. OpenSky is about clean, traceable data that scientists use to study flight paths, emissions or the quality of positioning methods, for example.

Where the data comes from

The foundation is the same as for any community flight tracker: ADS-B. Aircraft determine their position by satellite navigation and regularly broadcast it, together with altitude, speed and identifier, on the 1090 MHz frequency. Anyone with a suitable antenna and receiver can pick up these signals. How this works technically is explained in the guide flight tracking with ADS-B for spotters; the differences between the transponder modes are covered in Mode S and transponders explained.

OpenSky listens to the entire Mode S downlink on 1090 MHz, so not just to the ADS-B position reports. According to OpenSky, three more sources come on top:

• FLARM: the collision warning system of many gliders and light aircraft, fed in through receivers of the Open Glider Network. More in the article on FLARM and the Open Glider Network.
• ADS-C: position reports that aircraft send over a satellite data link, mainly on oceanic and long-haul routes. They are sparse and mostly come from cruise altitude.
• VHF voice radio: recorded as part of a research project on automatic speech recognition in aircraft radio.

One special feature: for every message, OpenSky also stores physical-layer data, such as the times of reception at each receiver. This makes the archive valuable for researchers who want to advance positioning methods such as multilateration (MLAT). Each aircraft identifies itself through its ICAO 24-bit address, called “icao24” in OpenSky.

What OpenSky doesn’t know

Before you use OpenSky for your spotting planning, you should know its limits. They follow directly from the data model:

• No schedule data: OpenSky doesn’t match the tracks to commercial schedules. There are no scheduled departure times, cancellations, delays, scheduled flight numbers or passenger counts. What you see is the callsign from the transponder.
• Departure and arrival only the next day: Departure and arrival airports are derived in a nightly run from the finished tracks of the previous day (UTC). For the current day, this assignment isn’t available through the flight queries.
• No MLAT: Aircraft that transmit only Mode S without a position don’t appear on the map. This also affects some military aircraft.
• Uneven coverage: OpenSky is best in Europe and the US. Low-flying traffic is only visible where a receiver is nearby.
• Aircraft reference data only to a limited extent: The in-house aircraft database (registration, type, owner) isn’t always up to date. For current fleet information, the sources in the article fleet databases at a glance are better suited.

The live map: Flight Map and OpenSky Explorer

The “Flight Map” menu item takes you to the live view. It shows all aircraft whose positions the network is currently receiving and can be searched by identifier or callsign. Compared with the big commercial flight trackers, it is plainer: no photos, no schedule info, no arrival predictions. In return you get the raw values as they arrive in the network.

For everyday spotting, the map is therefore more of a secondary tool. It gets interesting when you want to check whether an aircraft is received in a certain area at all, or when you want to compare the data with another service. If you’re looking for unfiltered community data with a mature map interface, you’re better off with ADS-B Exchange or the community trackers adsb.fi and adsb.lol.

Besides the map, the OpenSky site has other public views worth a look:

• Network Coverage: a coverage map showing where, and down to what altitude, the network receives aircraft.
• Alerts: a list of detected emergency squawks such as 7700 (emergency), 7600 (radio failure) and 7500 (hijacking). What’s behind the codes is explained in the article squawk codes 7500, 7600 and 7700.
• Top Lists: rankings of the receivers, for example by number of messages and aircraft received.

The REST API: query flight data yourself

OpenSky gets really interesting for anyone who likes to tinker with data. The public REST API delivers so-called state vectors: records that, for one aircraft at one point in time, contain among other things identifier, callsign, country of registration, position, barometric and geometric altitude, ground status, speed, heading, climb or sink rate, squawk and the source of the position. Fields without a current value stay empty: if no position report has come in for more than 15 seconds, the position is missing, and an aircraft with no new report at all drops off the list after that time.

Besides the state data, the API offers further queries:

Query	What you get	Limits according to the documentation
/states/all	current state data, optionally filtered to an area or individual identifiers	anonymous: only current data at 10-second resolution; with an account up to 1 hour back at 5-second resolution
/states/own	data from your own receivers only	costs no credits, sign-in required
/flights/aircraft	flights of a specific aircraft	query period at most 2 days, data only up to the previous day
/flights/arrival and /flights/departure	arrivals and departures at an airport (ICAO code)	from the nightly run, so only past days
/flights/all	all flights in a time window	query period at most 2 hours
/tracks	waypoints of a flight path	marked as experimental, up to 30 days back

For airport queries you need the four-letter ICAO code, so EDDF rather than FRA. The difference is explained in the article IATA and ICAO codes.

Credits and sign-in

The API works with daily quotas in credits, separate for state data, flights and tracks. As of October 2026, these tiers apply according to the OpenSky documentation:

A /states/all query costs between one and four credits, depending on the size of the area queried. When the quota is used up, the server responds with error code 429 and tells you when you can try again. Important for anyone using old scripts: since March 18, 2026, OpenSky no longer accepts sign-in with a username and password. Instead, you create an API client in your account and use client ID and client secret to get an access token (OAuth2 client credentials) that expires after 30 minutes. Official libraries exist for Python and Java, though according to OpenSky the Java version now serves only as an example. OpenSky lists further community tools on a page of its own.

Historical data: Trino and public datasets

The heart of OpenSky is the archive. The complete data set can be accessed through a SQL-like interface based on Trino. OpenSky grants full access to research institutions, aviation authorities and government agencies. Private learning and hobby projects generally don’t qualify. Access is enabled separately on request.

As an individual you’re still not shut out. OpenSky publishes a series of scientific datasets that anyone can download. A few examples from the datasets page:

• Weekly 24-hour snapshots 2017 to 2022: complete state data for one day per week, split into hourly files.
• COVID-19 flight dataset: cleaned flights from early 2019 on. Well suited to tracing the slump and recovery of air traffic.
• Raw data samples and the LocaRDS dataset: for anyone interested in positioning methods and the technology behind the signals.
• Further special datasets, for example on ADS-C messages.

If you simply want to know where a particular aircraft has been over the last few weeks, the commercial services are often more convenient. The article retrieving an aircraft’s flight history describes the options. And how to complete your own sightings afterward with track data is shown in matching sightings with ADS-B.

Research with OpenSky data

What is all this for? Originally the founders wanted to improve the safety and reliability of airspace use, for instance by examining weaknesses of ADS-B. The foundational paper “Bringing Up OpenSky” appeared in 2014; anyone using the data scientifically is supposed to cite exactly this work. Today the range of topics runs from flight path prediction through noise and emissions studies to positioning research. Several hundred scientific publications are now based on OpenSky data, and the community meets every year at a symposium of its own.

The data is also used outside science. Journalists use it to investigate unusual flight movements, for example, and organizations and international institutions also analyze air traffic with OpenSky data. Even in data competitions run in the circle of the European air navigation organization Eurocontrol, OpenSky flight paths are used.

Becoming a feeder yourself

The most direct way to use OpenSky and give something back at the same time is your own receiver. The basic setup is the same as for other networks: a Raspberry Pi, an RTL-SDR stick, an antenna for 1090 MHz, a stable power supply and a permanent internet connection. The location should be as high as possible with a clear view in all directions. You’ll find tips in building your own ADS-B receiver and antenna location and mounting.

Ready-made multi-feeder images such as the one from adsb.im are convenient for beginners: through a web interface you feed several networks at once without needing the command line. If you already have a working dump1090, you can install OpenSky’s feeder software instead. How to serve several networks in parallel is shown in feeding multiple networks with Ultrafeeder, and what other networks offer their feeders is compared in feeder programs compared.

So that OpenSky assigns your station to your account, you link it to your OpenSky user account during setup. Client ID and secret from the API area aren’t meant for this; they belong to the REST API.

What feeding gets you

Once your receiver has been online at least 30 percent of the time in the current month, you count as an active feeder and your API quota rises to 8,000 credits per day. You don’t have to apply for anything; OpenSky recalculates the status regularly, so the change can take a little while. Whether receiving and passing on the data is legally unproblematic for you is covered in the article Is sharing ADS-B data allowed?.

Terms of use: what’s allowed

The OpenSky data is freely accessible, but not free of rules. The most important points from the documentation and terms of use, as of October 2026:

• The API is for research and non-commercial use. A private dashboard, an analysis of your home airport or a learning project fit that.
• Commercial use requires a license. Anyone who wants to use live flight data for commercial purposes or in a product must agree with OpenSky beforehand. If in doubt, read the terms of use carefully.
• Credit the source. Anyone who publishes OpenSky data names the network as the source; scientific work cites the 2014 paper.
• No multiple accounts. Anyone who creates several accounts to get around the rules risks a permanent ban of all accounts. OpenSky can block requests from the networks of large cloud providers because of abuse.

OpenSky compared with other services

Feature	OpenSky Network	Commercial flight trackers	Community trackers such as ADS-B Exchange
Operator	nonprofit association	company	community projects or companies
Focus	research and data archive	live view for travelers and fans	unfiltered live data
Schedule data	no	yes	limited
MLAT	not currently	yes	yes
Historical data	large archive, full access for research	depends on subscription	depends on service
Reward for feeders	higher API quota	usually premium subscription	depends on service

For everyday spotting at the fence, a classic flight tracker is usually the faster tool; you’ll find details under Flightradar24 vs. FlightAware. OpenSky plays to its strengths when you really want to understand data and analyze it yourself.

Conclusion

The OpenSky Network is the counterpart to the colorful flight tracker apps: less convenience, but open, well-documented data and an archive that reaches back to 2013. For spotters, the REST API for small analyses of your own, the freely downloadable datasets and – if you have an antenna on the roof anyway – feeding for a higher quota are the most worthwhile. Full archive access, however, goes only to research, and anyone who wants to make money with the data needs a license.