I’m not sure if I’ve talked about scale before but here goes anyway. BFG works around an approximate scale of 1cm=1000KM for the planets and other tabletop features. Obviously this means the ship models are massively out of scale, an Imperial cruiser is NOT 9000KM+ long! The scale is basically there as a rule of thumb and I didn’t worry about it too much when it came down to setting weapon ranges, ship speeds and so on. These were all done to create the right impression of distance on the tabletop. For example 60cm ‘feels’ like a long way and 30cm doesn’t, the weapon ranges aren’t defined by some pseudo-science calaculation of the energy dissipation rate of lasers (fairly obviously ) but to create an interaction between the (massively out of scale) models on the tabletop.
The more interesting question is perhaps how long is a turn, and that one I don’t know the answer too – I’d guess somewhere between 15 minutes and an hour (quite likely telescoping so that at long range a turn is an hour but by the time you’re within 15 cm its 15 minutes). This would make an attack craft capable of moving 30cm per ordnance phase capable of doing approximately 30-120,000 km/h. I’ve got no idea if this is realistic for starfighter speeds, or unfeasibly fast, incredibly slow or what , perhaps someone on the list could enlighten us all on this front (don’t just tell us what it says it the Star Wars technical manual though!).