Hence “some part of a value.” Such as weight=plane+fuel+people+luggage. If one of the variables became 0 you’d still have the other 3. It was a low enough va

Hence “some part of a value.” Such as weight=plane+fuel+people+luggage. If one of the variables became 0 you’d still have the other 3. It was a low enough value to have made multiple pilots question its value that day, like fuel or passenger load was missing completely.