Update: Added caveat about flights operated by other carriers
Originally Posted by
dstan
• How much carry-on baggage can I bring aboard?
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If the first segment in your itinerary is on a flight operated by another carrier, including AA codeshare flights, then the carry-on baggage rules of the operating carrier apply at check-in. Note that many carriers restrict the weight of carry-on baggage considerably more than AA and may weigh your carry-on bags at check-in.