Don't know about radarbox but having seen Flightradar24 demonstrating flight congestion on BBC news earlier on I had a look at that. Useful amount of usability on the free version even if you need to refresh it every half hour or so, and it returns to what you were looking at. Having followed a flight from Liverpool John Lennon which happened to pass near my house which I heard above the cloud cover dead on time with the screen info I was suitably impressed. Some experimentation showed info on military and private flights too. No doubt it has its drawbacks for the cognoscenti but it's all new to me. Might be tempted to go for the paid version sometime in the future.