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Yes, a 3.38-fl-oz (100 ml) container is allowed in carry-on under the 3-1-1 rule, as long as it fits in your single quart-size liquids bag.

Yes, WestJet lets you bring one carry-on plus one personal item; a small backpack counts as the personal item if it fits under the seat.

Yes, on American you can add your Known Traveler Number after check-in, then reissue your boarding pass to get TSA PreCheck if you’re eligible.

Yes — tasers can be in checked luggage if disabled, with battery rules applied and airline or country limits respected.

Yes, you can add baggage after check-in, but fees rise and each airline sets strict cut-offs online, at kiosks, or at airport counters.

Yes—one-way hold luggage on easyJet is only sold at the airport; online adds a bag to every flight on your booking.

Yes, most airlines let you buy a second adjacent seat (“extra seat”) for comfort or to secure an item, if fare and safety rules are met.

Yes, TSA PreCheck enrollment is offered at many airports through authorized centers; bring valid ID and finish a brief in-person visit.

Yes—late hotel check-in is usually fine if your reservation is guaranteed and you tell the hotel, or you risk a no-show fee and canceled nights.

Yes — adding checked baggage after check-in is allowed; some airlines let you do it online, others only at the airport with higher time-based fees.