Hi,
I think that the quick planner is just that - it does not (it cannot) take into account en-route winds. Did you encounter high head winds en-route ? 3 hours for that distance tells me you did - e.g. I did 1320 nm the other day outbound was 3hrs 30min and return 3hrs 15min. I loaded around 10.6 tons for outbound and 10.1 for inbound. Zfw was 45 out, 44 inbound.
Do you have access to a planner that can calculate even the time needed based on en-route headwinds as that should be your starting point. To add to this, the distance is not air-distance - as I began to explain with the example, winds do play a huge factor in determining your flight time and therefore your fuel that you need. I've experienced simulated flights just from uk to Egypt and return that vary in time taken by an hour (half an hour quicker going and half an hour longer on the way back).
- Carl