Using 'do' unnecessarily

Solution 1:

The auxiliary verbs do and does can be used before a bare infinitive to add emphasis to a sentence. The fact that we're using the infinitive becomes more apparent in the third person.

If he does have any questions, he can ask the attendant.

If he has any questions, he can ask the attendant.

The words do and does are accented when spoken. This serves as a kind of auditory cue to pay close attention to the phrase that follows. A useful way of adding emphasis.

After reading Janus's explanation, it seems another question is why are there so many dos and accented helper words. I think this is because the flight attendant, who is talking over the speaker, has only a few things to say but wants to make sure each is understood. It's not a conversation, but rather a few announcements.

An analogy would be when someone presents information as a list. We use the words "first", "second", "third", or "next", "finally", etc. to create order and delineation. In the same way, the flight attendant is using stress and pitch to create delineation, by accenting certain helper words like do, will, etc.