Regulations may differ among airlines. In general, carry-on luggage should be able to fit in the plane's overhead compartment or below a passenger's seat. Most airlines also allow their passengers to board with a purse, briefcase, computer or another small tote bag.
Generally, carry-on luggage should be no wider than 14 inches, no deeper than 9 inches and no taller than 22 inches. American Airlines will allow carry-on luggage that does not exceed 45 linear inches, or length plus width plus height. Continental Airlines allows carry-on luggage that does not exceed 45 linear inches. United Airlines allows carry-on luggage that measures 22 by 14 by 9 inches or less.
Most airlines set weight limits on passenger carry-on luggage. American Airlines sets a 40-pound limit on passenger carry-on luggage. Continental Airlines and United Airlines also allow carry-on luggage that does not exceed 40 pounds.