Enhanced security measures at U.S. airports now prevent air travelers from placing most liquids, gels, lotions and similar items in their carry-on luggage.
Those items must be put in the checked luggage in the plane's cargo hold.
The new security measures were imposed August 10, after British authorities announced they had broken up an alleged plot to blow up U.S.-bound airliners over the Atlantic Ocean.
Passengers boarding planes at U.S. airports are still allowed to carry on certain prescription medicines in liquid form, and certain non-prescription items like eye drops in small bottles.
Baby formula and food, as well as breast milk, are allowed on board if the child is traveling on the plane.
Duty-free items initially were prohibited under the new regulations. But the rules have since been modified so items bought at duty-free shops can be brought on board a plane by store personnel.
International travelers arriving in the United States who are scheduled to board a connecting flight must put all liquids and gels, including duty-free items, into their checked baggage.
British authorities on August 10 banned all passengers from bringing carry-on items aboard aircraft. But they have since modified the rules to allow one small carry-on bag that does not contain liquids, gels lotions or similar items.
The only exceptions are prescription medicines, baby milk and liquid baby food.
Some information for this report was provided by AFP, AP and Reuters.