If anybody wants to play with the routes I've gathered using PlanePlotter and Flight Display 6 for the central UK, then I'll make the file available.
However, you will either have to add these routes manually, or will need to know how to import them to the NavData.db3 database as described by tarbat - easy when you know how, but has the potential to go horribly wrong :-0
Here is a small section of the csv file - note the capture of Flight ID's with letters after the numbers. EZY24 might already be in the RadarBox flight database, but EZY24LC certainly won't be, even though the route is the same as for EZY24
"EZY24LC","EGGW","EGPD"
"EZY265","EGSS","EGAA"
"EZY26QD","EGSS","EGAA"
"EZY27AJ","EGKK","EGAA"
"EZY27VE","EGSS","EGPF"
"EZY28EJ","EGKK","EGAA"
"EZY28ZF","EGSS","EGPH"
"EZY2LN","EGGD","EGAA"
"EZY302T","LSGG","EGGP"
"EZY305K","EGGP","LSGG"
"EZY3075","EGSS","LEAS"
"EZY309U","EGGP","LSGG"
"EZY31WB","EGGW","EGPH"
"EZY32HL","EGKK","EGPF"
I've captured 788 routes so far, but the majority of these will already be in the RadarBox database.