Guide

Flying with a lap infant: the rules and the safer option

US rules let a child under two fly on an adult's lap without a seat of their own. It is legal, it is often cheaper, and the Federal Aviation Administration still recommends against it. This guide covers the age rule, what the FAA advises, how car seats on planes work, and what to expect at security and on the booking.

Last verified 16 October 2026Source: FAA: Flying with children

The age rule

The rule for US airlines is in 14 CFR 121.311. Every passenger who has reached their second birthday needs their own approved seat and seatbelt. A child who has not reached their second birthday may instead be held by an adult who is in an approved seat, provided the child is not in any restraining device during taxi, take-off and landing.

Three consequences follow:

• The cut-off is the second birthday, on the day of each flight. If a child turns two during the trip, the flights after the birthday need a seat for the child. Book that leg with a seat from the start; changing later can be awkward.
• One lap child per adult. The rule is built around an adult holding a child, and airlines generally allow one lap infant per adult; check yours. In practice an adult travelling alone with twins should expect to buy a seat for one of them.
• Lap-held belts and harnesses are out for take-off and landing. The regulation does not allow lap-held child restraints, vests, harnesses or booster seats during taxi, take-off and landing.

What the FAA actually recommends

The FAA's own guidance for parents is direct: the safest place for a child under two on a US airplane is in an approved child restraint system or device, not on a lap, because arms cannot hold a child securely in unexpected turbulence. The FAA strongly urges parents to secure young children in an approved restraint for the whole flight and notes that buying a seat is the only way to guarantee you can use one. It does not require it, which is why lap travel remains an option.

Our honest view as booking agents: on a short domestic hop, many families choose a lap seat and that is a legal, common choice. On a long flight, an overnight flight, or a route known for turbulence, a purchased seat with an approved car seat is safer and usually easier for everyone.

Using a car seat on board

A car seat (the FAA calls it a child restraint system, or CRS) can be used on board if it is approved for aircraft. Look for the label. Seats made to US standards since 26 February 1985 must carry two statements, one of which reads, in red lettering, that the restraint is certified for use in motor vehicles and aircraft. Seats approved by a foreign government or made to United Nations standards carry their own markings.

• The airline cannot refuse an approved seat if the child has a ticketed seat (or the airline makes a seat available) and a parent or guardian is travelling, under 121.311(c). It can decide where on the aircraft the seat goes.
• If the approved seat does not fit the assigned aircraft seat, the FAA says the airline is responsible for accommodating it in another seat in the same class of service.
• Check the width before you fly. Read the car seat manual to confirm it can be secured with a lap belt; if it cannot be installed properly, you may be asked to check it.
• An alternative for older toddlers. The FAA describes an aircraft-only harness device (CARES) certified for children who sit upright alone, weigh 22 to 44 pounds and are up to 40 inches tall, used in their own seat. It warns about counterfeits sold online.

Where you can and cannot sit

You cannot sit in an emergency exit row with a lap infant. US rules on exit seating (14 CFR 121.585) exclude anyone whose responsibilities, such as caring for small children, might prevent them performing the exit functions. Airlines also set their own limits on where lap infants can sit and how many can share a row, so families may be moved when seats are assigned. Choosing seats early, or asking the airline to seat a young child next to a parent, avoids most of the last-minute shuffling.

At the security checkpoint

TSA's published procedures for travelling with children cover the main points:

• No ID is required for under-18s travelling within the US, according to TSA. Airlines can set their own rules, and many ask for proof of age for a lap infant, such as a birth certificate, so carry one.
• Carry the infant through the metal detector. Children come out of strollers and car seats; strollers, car seats and carriers go through the X-ray or are inspected by hand. TSA says an infant may be carried in a sling or carrier through the walk-through detector, though that can lead to additional screening.
• Formula, breast milk and baby food are exempt from the 3.4-ounce limit in reasonable quantities, as are ice packs to keep them cool. Tell the officer at the start and take them out for separate screening. More detail is in our TSA liquids rule guide.

International trips

A lap infant on an international flight is still an international passenger. A US citizen of any age needs their own passport to fly internationally, and the destination country may require a visa or entry authorisation for the baby too. If only one parent is travelling, carry evidence of the other parent's consent; some countries ask for it at the border. International lap fares are usually not free: airlines commonly charge a portion of the adult fare plus taxes, so ask for the total when you book. US domestic lap travel is normally free of a fare, but not always free of charges on every airline.

For identity documents for older children and adults, see ID requirements for US domestic flights. If the child will travel without you at an older age, see booking a child travelling alone.

Booking a lap infant: a short checklist

1. Add the infant to the booking at the time you book, with their name and date of birth. A lap infant is not automatically "on" an adult's ticket.
2. Check each leg against the second birthday.
3. Ask about the stroller and car seat allowance. Most US airlines carry them without charge, but rules differ; our baggage fees guide links to each airline's page.
4. Decide on a seat versus a lap with the FAA's advice in mind, especially for long flights.
5. Pack the paperwork: proof of age, passport for international trips, and consent letter if one parent travels alone.

Common questions

Sources

• FAA: Flying with children (Kids' Corner and tips for parents)
• FAA FAQ: Does the FAA require children to be in child restraint systems?
• 14 CFR 121.311, Seats, safety belts and shoulder harnesses (eCFR)
• 14 CFR 121.585, Exit seating (eCFR)
• TSA: Traveling with children
• TSA: Acceptable identification at the checkpoint
• US Department of State: Passports

General information, not safety or legal advice about your situation. Trailisse is an independent travel agency; the FAA, TSA and your airline are the authority.