English: One moment please. I'm going to check.
French: Un moment SVP. Je vais vérifier.
"One moment please" "Un moment SVP" is a very common phrase you'll use as a flight attendant. There's no more space to stow a passenger's suitcase so you say "un moment SVP" as you go find an agent to tag the bag. A passenger would like to hand you something to throw out, but your hands are full, so you say "un moment SVP" indicating that you'll return shortly. You ask a passenger what they'd like to drink and they want coffee. You've just run out and your colleague has gone to brew more, so you tell the passenger "un moment SVP".
If a passenger asks you if you have something (an extra customs form, a blanket, a pillow, earphones, a snack, a drink, etc.) and you need a moment to go retrieve it, you can say "un moment SVP." If you're not sure if you have any, or if you have any left, you can add "I'm going to check" "Je vais vérifier".
Je vais=I'm going
Vérifier=to check, to verify
-Avez-vous des sandwichs?
-Un moment SVP. Je vais vérifier.
You should use "vérifier", but you may also hear your francophone colleagues or passengers say "checker" or "tchéquer", which is an anglicism of "to check".
Want to learn to speak the French you need to work as a flight attendant? Learn even more with Canadian French for Flight Attendants.