We’ve never had to show ID for our infant son before a domestic flight. But parents traveling with infants for the first time should expect scrutiny nonetheless. Transportation Security Administration (TSA) agents are well within their rights to ask parents to produce birth certificates or adoption paperwork for infants and very small children without ID of their own. We did bring our son’s birth certificate on his first flight. After that, it wasn’t necessary. Upon our return from that trip, we applied for a passport for the little guy knowing we’d need it for an international vacation set for later that year. On international flights, you must present your child’s passport, so make sure you get one as soon as you set your travel dates. Our kid’s passport came within six weeks, but the State Department recommends allowing at least eight weeks, though you can expedite delivery for an additional fee. Expect to pay a little under $100 for a nonexpedited passport, including photography.