Flightradar24 provided receiver.
The receiver needs a bidirectional connection on port UDP/443 to IP 185.218.24.61.
In a normal home, this is not required.
If you are in a more complex network, you might need to configure the firewall to allow this connection. Ideally, whitelist the entire subnet 185.218.24.0/22 as IPs might be moved around.
Self built setup.
If you have built your own receiver, and you are behind a firewall, you will need to open these outgoing ports for the feed.
80 TCP 443 UDP/TCP 19788 UDP/TCP 8099 UDP/TCP 123 UDP/TCP 53 UDP
Please also whitelist our domains
*.fr24.com *.flightradar24.com