My journey times entered in IVAO Pireps are always significantly longer than those predicted in the FSC flight plan. That can be a nuisance if I want to start a flight with the idea of arriving at a specific time; say just before I'm expected to join SWMBO in watching a programme I "wouldn't want to miss"!
It's been fairly simple to modify the Lotus spreadsheet I put together to calculate fuel loads. It now calculates, then adds in, taxi times, time climbing to and descending from altitude, plus final approach and landing, then adding these to time in the cruise. All of these are at different speeds and I'm guessing that the FSC designer has just taken total distance and divided by cruise speed.
Even the more realistic stage by stage approach makes no allowance for winds. I might be able to build that in but it will probably make my head ache; even more.
BTW, does anyone else still use Lotus? Gerry Winskill