Tip: Children Under 18 With an Adult Don't Need ID to Get Through Security
In addition to a boarding pass, there's one other credential adults need to get through airport security: personal identification. But, that's not the case for travelers under the age of 18 if they're with an adult.
If someone under 18 is traveling with an adult companion in the US, they don't need one of the government-issued ID documents in order to get through security — they just need a boarding pass. That's right, your child just needs a boarding pass to get past the TSA checkpoint.
For those older than 18, there is a requirement of showing valid identification at the airport. On the TSA's website, there are 16 examples of valid identification, including a driver's license, US passport, US military ID, permanent resident card, foreign government-issued passport and more. To see the full list, check out the TSA's website.
Keep in mind that the TSA recommends contacting your airline for specific ID requirements for travelers under 18. For example, American's website says that you may be required to present proof of age for any children under the age of 18, and United's site says that children under 18 traveling with an adult are not required to show ID at time of check-in. As the TSA says, it's best to check with your airline for specific requirements.