If FAID is not "scientifically based", what is? Genuinely interested..
Interesting question. I think the answer is airlines buy FAID/FAST off the shelf turn it on and away you go. However there is no scientific validation e.g. mapping of rosters, crews wearing motion watches etc etc as it could be seen a one size fits all system. Neither system looks at cumulative fatigue well either.
In the UK BALPA are looking at all these systems under review by a scientific body