English: Can you stow your bag?
French: Pouvez-vous ranger votre sac?
Flight attendants are in charge of cabin safety. Part of that task is to ask passengers to stow their bags, turn off their electronics, stow their table trays, etc. for take-off and landing.
Just like in English, there are several ways in French to politely ask someone to do something.
One way is to ask "can you?" "pouvez-vous?"
"Pouvez-vous ranger votre sac SVP?"
Vous pouvez=you can
Votre sac=your bag
SVP (s'il vous plaît)=please
More importantly, remember that politeness is also communicated non-verbally, through body language, facial expressions, voice intonation, etc. Thus, it's equally, if not more important to communicate politeness through your smile, eye-contact, body language, and voice tone, as you ask them "pouvez-vous ranger votre sac SVP?"
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