IO540,
I think a BIG mistake is to get attached to the word "airway". This is a peculiar UK PPL tradition, where instructors use the word "airway" to basically scare students into avoiding Class A airspace. In much of southern Europe, you fly VFR on published airways (IFR routes), because that's where their simple-minded ATC expect to see traffic.
The biggest mistakes are to muddy the waters/answers with irrelevancies or info that's incorrect rather than just answering the original question(s) being asked.