Since its launch in 2013, the OpenSky Network has quickly evolved to a large-scale air traffic control data collection and sharing platform. With more than 4000 sensors registered across the globe and more than 25000 users, the OpenSky Network is greatly contributing towards the vision of a more efficient, secure, and reliable operation of the airspace by providing open accessibility of air traffic control data to the public.

Following the successful events in past years, we are proud to announce the Ninth OpenSky Symposium. The two-day event will be hosted by EUROCONTROL in their headquarters in Brussels (Belgium) in November 2021 and is sponsored by the Performance Review Commission (PRC) of EUROCONTROL. The PRC aims to establish an Open Performance Data platform available in cooperation with Opensky Network and its community.

The event is targeted at anyone interested in data-based aviation research. The Symposium will serve as a forum to discuss new ideas, the network itself, and research activities around OpenSky. Participants are invited to actively contribute to the program by presenting their projects at the Symposium. In the past years, the symposium attracted a diverse and interesting audience from research, authorities, and industry.

Depending on the situation of the COVID-19 pandemic, we hope to have a hybrid format with possibilities of both on-site and online presence. There will be many opportunities to get to know the community during the social activities around the Symposium program.

The websites of previous workshops can be found here:

• 2015, Oxford, United Kingdom
• 2016, Oxford, United Kingdom
• 2017, Kaiserslautern, Germany
• 2018, Frankfurt, Germany
• 2019, Zurich, Switzerland
• 2020, Virtual (Eurocontrol)

Authors can submit their abstracts and papers at: https://easychair.org/conferences/?conf=opensky21

The submissions consist of:

1. Abstract: submissions describing the idea of the work and presentation that will be given at the symposium. Abstracts should have a length of 1-2 pages and are due by September 10, 2021, at 23:59 (UTC-12).
2. Paper: submissions describing and explaining the work in more detail. Papers should be 6-9 pages long and are due by November 12, 2021.

Please ensure that your submissions are PDF files of a maximum of 2 pages (Abstract) and 9 pages (Papers), including references and appendices.

Submissions should closely follow the instructions given for the MDPI Proceedings template here. We recommend using Overleaf which includes MDPI article template files. Abstract submissions may be anonymous (i.e., papers do not contain author names or affiliations), but author names and affiliations must be part of the paper submissions.

The EasyChair system will be used for collecting submissions, providing reviewer feedback, and notifications. Please visit https://easychair.org/cfp/opensky21 for further information.

To attend the conference in person, you must be able to show your valid COVID certificates (e.g, EU Digital COVID Certificate).

The registration fees are*: