To feed Flaghtaware, you need to install either dump1090-fa or dump1090-mutability. The Flightradar24’s Pi24 image has integral dump1090 (malcolm robson), which cannot handle Flightaware’s mlat.
Another problem with Pi24 image is that lighttpd fails after reboot.
Using Flightradar24’s Pi24 image to feed Flightaware means unnecessary trouble and workarounds. This I have mentioned clearly in the thread “feeding data to multiple sites - a brief guide”.
Best option is to write either Raspbian image or Piaware image to your micoSD card. Please go to thread “Bake a Pi” , and choose any one of the 3 options ( OPTION-1 or OPTION-2 or OPTION-3 ), and after completing all steps in one of these options, add Flightradar24 Feeder as shown in item (2) of post “ADDITIONAL DATA FEEDERS” of “Bake a Pi” thread.