Yeah, fair. Stupid way of asking. Sorry.
So let's get more detailed:
curl -s "https://USERNAME:PASSWORD@opensky-network.org/api/flights/aircraft?icao24=3c675a&begin=1517184000&end=1517270400" | python -m json.tool
Works, I get a response. So I look at /states/all and see that there's a plane, a41b89. So I try the following:
curl -s "https://U:P@opensky-network.org/api/flights/aircraft?icao24=a41b89a&begin=1616532498&end=1616532502" | python -m json.tool
I get [] (and see it's a 404 if I -v the curl).
Maybe I don't understand how the data works