Q. I plan to fly with my 16-month-old twins. Do they need a reservation? How do I make sure they can fly with me when I reserve a ticket for my husband and myself?

A. If traveling domestically, your infants, because they're under two years old, do not need to buy a separate fare and you don't need to inform your airline beforehand that they'll be traveling with you. They can be considered lap children, which means they must sit in your laps for the entire flight. While this is "legal," you should consider that modern jetliners take off and land at high speeds (80-100 miles per hour or more), and they can decelerate just as quickly. You wouldn't put a baby in your lap while driving your own car, even if traveling just 15 or 20 miles per hour (in fact, it's illegal); you'd put them in a car seat. So I really don't recommend seating your children in a speeding jet airplane in any other way. If the plane stops suddenly, your child will become a projectile, and infants have indeed been injured in such circumstances, and also during extreme turbulence. Also, it's incredibly uncomfortable having a baby in your lap on a long flight. Keep in mind that if you're traveling internationally, you'll generally be required to pay ten percent of the applicable adult fare for your lap children (even if you're flying on a frequent flyer ticket), so you'll need to inform your airline that they'll be flying with you when you buy your own fare.