One thing that has not changed is the requirement to carry a photo ID. If you are flying within the United States and are age 18 or over, you must carry a government issued photo ID, driver's license, passport or other acceptable document. Photocopies are not accepted, so the original document must be presented. Children less than 18 years of age do not need to carry a photo ID.

If you are traveling outside the United States, check the requirements carefully. You will generally need to have your passport; or birth certificate along with a photo ID. Your passport will need to be valid at least through the period of your stay. The temporary rule that allowed you to carry a copy of the passport application no longer applies; you must have the actual passport.

Several countries, particularly the Caribbean islands, will accept other documents, such as a birth certificate and driver's license, instead of a passport. If you are traveling to a country that accepts a birth certificate, it has to be the original copy or a certified copy. A US alien registration card, in some instances, is considered to be an acceptable form of photo ID as well as a driver's license.

Other countries require the passenger to obtain a visa in advance and some countries even require you to have "sufficient funds" for your trip, as well as a ticket to return from that country. Depending on your destination, you may be required to verify where you are staying. Also, if you are a child traveling with just one parent, you may need a letter of consent from the other parent.

Most airlines allow you to take a carry on bag as well as a personal item - a laptop, purse or camera, for example. The exact size of the carry on bag may vary by airline but in general, it should be able to fit under the seat in front of you or in the overhead compartment. The maximum weight limit on the carry on bag is usually around 40 pounds; the maximum size 45 linear inches.

Perhaps nothing is quite as confusing as the rules concerning carrying liquids on to the plane. Any liquids, lotions, creams or gels that you have in your carry on bag must all be in containers holding 3 ounces or less, and the containers must be able to fit in a one quart size Ziploc type bag. The plastic bag then has to be passed through the X-ray screening device separately. If you have liquids in larger containers or too many to fit in the bag, they must go in your checked luggage.

Medication and baby formula is generally exempt from the 3 ounce rule, as well as liquids necessary to sustain life, such as any liquids used for carrying transplant organs or bone marrow. Obviously this does not apply to the every-day traveler. If you carry-on medication, it should be in the original labeled container and it's also a good idea to take a prescription or doctor's note. You cannot carry a drink on to the plane with you unless you purchased it after passing through the security checkpoint.

Almost equally confusing is the list of things that you can and cannot take on board the plane in your carry-on bag. Items that are obviously dangerous or could be used as a weapon, such as long knives, explosives, guns or large tools, of course cannot be taken on an airplane. You are allowed to carry on to the plane items such as safety razors, scissors with blades shorter than 4 inches and cigarette lighters.

The rules concerning checked bags can vary depending on the specific airline. Also, if you are traveling in coach or first class and whether or not you are traveling overseas can impact rules as well. In general, you are allowed two pieces of checked luggage, each weighing no more than 50 pounds and each measuring less than 62 linear inches. Every piece of checked luggage must be clearly labeled.

In general, the airlines advise you to check in at least 90 minutes for a domestic flight and at least two hours beforehand if traveling internationally. The airlines reserve the right to give your seat away if you have not checked in by a certain time - usually around 30 or 40 minutes before flight time. US airlines do not require you to reconfirm your flight beforehand, but it's a good thing to do.

So, if you are going to be flying, and especially if you have not been on an airplane recently, check the current rules with your airline or travel agent. You do not want to be one of the many people that are denied boarding their flight.