I recently introduced FlightGear 2019.1.1 (on Linux Mint 20) Last year (back on Linux Mint 19 omegle coomeet) I had FlightGear 2018 (I guess) and I didn't experience this issue.
The only planes I could really want are the EC-135 and Let-13 (Czechoslovakian lightweight flyer) and I tried downloading coomeet them from the FlightGear thread, but the downloads stopped without failure.
Well obliged for any help