Children under 18 don't need ID for US domestic flights, but do need their own passport abroad. Lap-infant proof of age, consent letters and unaccompanied-minor paperwork explained.
Cover image: Check-in counters at Suvarnabhumi International Airport, Bangkok — photo by User:Mattes, CC BY-SA 3.0, via Wikimedia Commons.
Children under 18 do not need any ID to fly domestically within the United States, according to the TSA — but they do need their own passport for any international flight, and a few situations (lap infants, kids flying alone, one-parent travel abroad) require extra paperwork. Here is exactly which documents cover which scenario, so nothing gets caught at the checkpoint or the gate.
The short version by scenario:
- Domestic US flight, child with an adult: no ID needed for the child; the accompanying adult needs a REAL ID-compliant license or an accepted alternative.
- Lap infant (under 2): no ticketed seat, but airlines ask for proof of age — bring a birth certificate.
- International flight: every child, including newborns, needs their own passport (plus a visa where required).
- Child flying alone: the airline's unaccompanied-minor form, plus proof of age and ID for whoever picks them up.
- Traveling without both parents abroad: a consent letter — preferably in English and notarized.
Do children need ID for domestic flights in the US?
No. The TSA is explicit: "Children under 18 do not need ID for domestic flights." The agency screens everyone, but a minor flying with an adult is not required to present identification at the checkpoint. There are two caveats worth knowing. First, if a child is flying alone and uses TSA PreCheck, they will need an acceptable ID to receive that screening lane. Second, the airline's rules are separate from the TSA's — carriers set their own requirements for unaccompanied minors, so always check with the carrier directly.
The adult traveling with the child is the one who needs paperwork. Passengers 18 and older must show valid identification at the checkpoint, and since the REAL ID deadline passed in May 2025, a state-issued REAL ID-compliant driver's license or ID card is the standard. Alternatives the TSA accepts include a US passport or passport card, Global Entry/NEXUS/SENTRI cards, a permanent resident card, a foreign government-issued passport, and a Department of Defense ID. Note that a temporary driver's license is explicitly not acceptable.
What documents does a lap infant need to fly?
Children under 2 can typically fly free on an adult's lap on US domestic flights, and while the TSA will not ask the baby for ID, the airline usually will ask you for proof the child really is under 2 — a birth certificate is the document of record. Travel writers who fly frequently with infants report being asked for it at check-in even for obviously young babies, and recommend carrying a certified copy or a clear photo of it on your phone. For international flights the exemption disappears: lap infants still need their own passport, and usually pay a percentage of the adult fare plus taxes.
What documents do children need for international flights?
Every US citizen child flying internationally needs a US passport — there is no age exemption, and both parents (or guardians) must appear with the child or provide consent when the passport is applied for. Depending on the destination, the child may also need a visa or an electronic travel authorization. For entry into the United States, the rule is the same in reverse: all children, including infants, must have their own passport or visa.
The one big exception is land and sea travel to Canada, Mexico and the Caribbean. Children under 16 crossing by land or sea can present a passport or an original or certified copy of their birth certificate, a Certificate of Naturalization, or a Consular Report of Birth Abroad. At 16 the concession ends — passport or Trusted Traveler card only. Flying to those same countries always requires a passport, for children and adults alike.
Do you need a consent letter to travel with a child alone?
If a child is leaving the country with only one parent, with a guardian, or alone, border authorities in many countries want evidence the trip is agreed by both parents — a measure aimed at international child abduction. USAGov advises a letter of consent, preferably written in English and notarized. If one custodial parent is traveling, the letter should come from the other parent; if the child is with a guardian or traveling alone, both parents should sign. The recommended wording is simple: "I acknowledge that my child is traveling outside the country with [the name of the adult] with my permission." Requirements differ by country, so contact the destination's embassy or consulate before you fly.
What do unaccompanied minors need to fly alone?
Most major US airlines run a fee-based unaccompanied-minor program — generally mandatory for ages 5 to 14 and optional for older teens, with specifics varying by carrier. Expect to provide the airline's unaccompanied-minor form, proof of age (birth certificate or passport) at check-in, and ID for the adult authorized to meet the child at the destination. The child keeps any customs and immigration documents with them throughout the journey. Book the service in advance: airlines cap the number of unaccompanied minors per flight, and connections are often restricted.
Children's travel documents by scenario
| Scenario | Child's documents | Adult's documents |
|---|---|---|
| Domestic US flight, with adult | None (TSA); birth certificate if under 2 on lap | REAL ID-compliant license or accepted alternative |
| Lap infant under 2, domestic | Proof of age — birth certificate | As above |
| International flight | Own passport (+ visa/eTA if required) | Passport; consent letter if other parent absent |
| Canada/Mexico by land or sea, under 16 | Passport or certified birth certificate / naturalization certificate | Passport or accepted WHTI document |
| Flying alone (unaccompanied minor) | UM form, proof of age, customs docs for international | Photo ID for drop-off and pickup adults |
| Non-US citizen child entering the US | Own passport and visa/authorization, including infants | Standard entry documents |
Practical checklist before you fly with kids
- Check passport validity — many countries require six months beyond your dates, and children's passports expire after five years (not ten).
- Carry the birth certificate even for domestic trips if your child is close to the two-year mark.
- Prepare the consent letter early enough to get it notarized.
- Arrive with buffer time — our guide to how early to get to the airport covers the timing, and families clearing border formalities in Europe should also read up on the EES entry/exit system, which biometrically enrolls non-EU nationals, children included.
- If your child is a frequent traveler, keep an eye on digital travel credentials — pilot programs may eventually spare families some paperwork.
Frequently asked questions
Do kids need ID to fly domestic in the US?
No. The TSA states that children under 18 do not need identification for domestic flights when traveling with an adult. The accompanying adult must show valid ID, and airlines may set their own rules for children flying alone.
Does a 2-year-old need a passport to fly?
Not for a domestic US flight — proof of age (a birth certificate) covers a lap child under 2. For any international flight, yes: a 2-year-old needs their own passport, even if they sit on your lap.
Can a child fly with a birth certificate instead of a passport?
Only on land or sea crossings to Canada, Mexico and the Caribbean, and only under 16. By air, a passport is always required for international travel.
Do both parents have to sign a child travel consent letter?
If the child is traveling with one custodial parent, the letter comes from the other parent. If the child travels with a guardian or alone, both parents should sign it. USAGov prefers the letter in English and notarized.
What ID does an adult need to fly with a child in the US?
A REAL ID-compliant driver's license or state ID, or an accepted alternative such as a US passport, passport card, trusted-traveler card or permanent resident card. Temporary driver's licenses are not accepted.
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