In the case of airline flying the sort of modis operandi rule was not to taxi if the gust factor, straight or cross, was greater than 50kts.
In the case of flying instructors, the 'limit', especially as it relates to training aircraft, appears in the handbook in order to afford instructors a convenient out when they feel that the pupil might be somewhat meteorologically challenged or when they, themselves, do not feel quite up to the sorties in the booking sheet?
