"Had been waiting" denotes the duration of your waiting before the plane landed so it is better as it is.
New words, one handy idiom, and a 2-minute quiz — delivered to your inbox to keep your streak alive.
khoshtipWe had been waiting for the plane an hour before it landed.Fine. A possible second version: We waited for the plane an hour before it landed. (Not were waiting. an hour is somewhat incompatible with the past continuous.)
khoshtipSo generally when we speak about duration of the time in the past we must use perfect continues tense, yeah?Not always. It depends on the context.
khoshtipSo generally when we speak about duration of the time in the past we must use the perfect continuous tenseNo, not at all. You can use any of these to speak about a duration of time:
khoshtipI can't accept your first example above, because of the "while".I understand this to mean that you don't believe that the verbs in that sentence signify extended activity through time.