GHB (gamma-hydroxybutyrate) is produced naturally in the human body in very small amounts. When taken as a recreational drug, and especially when taken in combination with alcohol or other drugs, GHB can be extremely dangerous. GHB is a central nervous system depressant.
International flights always allow carry-on luggage, but each airline has its own restrictions as to quantity, size and weight. Some international carry-on policies restrict bag weights to 11 lbs. or less, while domestic flights rarely have a weight limit.
Some airline-branded cards give you the benefit just for being a card-holder, though you have to consider whether it's worth paying the annual fee. As of June 1, holders of the Delta SkyMiles credit card from American Express can check a bag free on every Delta flight. With baggage fees of $25 each way, one would save $50 on a round-trip flight. On two or three trips a year, travelers' savings would cover the annual cost of a Delta SkyMiles Card: $95 a year for the gold version and $150 for the platinum edition.