The short version
- On U.S. domestic flights, babies under 2 can usually fly free on your lap with every major airline.
- International lap infants usually cost 10% of the adult fare plus taxes, but JetBlue and Southwest charge only taxes and fees.
- Strollers and car seats fly free on every airline below, checked at the counter or gate.
- The FAA says the safest place for a baby on a plane is an approved car seat in their own seat, not your lap.
Flying with a baby doesn't have to be expensive. Babies under two can fly free on a parent's lap on U.S. domestic flights, and every major airline lets you bring a stroller and car seat for free. Here are the lap infant rules for each airline as of November 2026, plus what to know about safety, documents and getting through security.
Lap infant rules by airline
| Airline | Domestic lap infant | International lap infant | Youngest age to fly |
|---|---|---|---|
| Delta | Free | Generally 10% of adult fare + taxes | No minimum; under 7 days needs a doctor's letter |
| American | Free | 10% of adult fare + taxes | 2 days; under 7 days needs a doctor's letter |
| United | Free | 10% of adult fare + taxes | 7 days |
| Southwest | Free | Taxes and fees only | 14 days |
| Alaska | Free | 10% of adult fare + taxes on long-haul routes | No minimum stated |
| JetBlue | Free | Taxes and fees only | 3 days |
All of these airlines treat a lap infant as a child under 2 for the whole trip. If your baby turns 2 before the return flight, you'll need to buy a seat for that leg. Policies change, so double-check with the airline when you book.
Airline-by-airline notes
Delta: a birth certificate may be requested at check-in. If you buy your baby a seat to use a car seat, it costs a regular fare; there's no infant discount.
American: babies can fly from 2 days old. Bring proof of age, such as a birth certificate or passport.
United: babies must be at least 7 days old. A birth certificate, passport or government ID works as proof of age.
Southwest: lap children must be at least 14 days old and travel with an adult who's 18 or older. Southwest requires proof of age, and it must be the original document or a photocopy. Photos or screenshots on your phone aren't accepted. Southwest moved to assigned seating in early 2026, so the old family boarding window no longer applies.
Alaska: may ask for a birth certificate or passport. Car seats and strollers check free, including some stroller wagons.
JetBlue: babies can fly from 3 days old. Car seats must go in a window seat (or a middle or aisle seat if the rest of the row is empty).
Lap infant or buy a seat?
A lap infant saves you a ticket, but here's how the FAA puts it: "The safest place for your child under the age of two on a U.S. airplane is in an approved child restraint system (CRS) or device, not in your lap." Your arms can't hold a baby securely in unexpected turbulence.
If you buy a seat, use a car seat labeled "This restraint is certified for use in motor vehicles and aircraft," and book a window seat. Buying a seat is the only way to guarantee you can use one. On a lightly booked flight you can also ask at the gate whether there's an empty seat next to you.
Bringing breast milk and formula through security
Breast milk, formula and juice are exempt from TSA's 3.4-ounce liquids rule, so you can bring more than you'd need for the flight in your carry-on, and it doesn't have to fit in your quart bag. Take them out of your bag for separate screening and let the officer know. Ice packs and gel packs to keep them cold are allowed too, and your baby doesn't even have to be traveling with you.
Free gear: strollers and car seats
Every airline in our table lets you check a stroller and a car seat for free, either at the ticket counter or at the gate. Gate-checking a stroller means you can use it right up to the plane door. A lap infant doesn't get a checked bag allowance of their own on most airlines, so pack baby's things in your bags.
Cheaper travel on the ground
Trains are often easier with little ones. On Amtrak, kids ages 2 to 12 ride half price and infants under 2 ride free on a parent's lap.
Heading to a theme park? Kids under 3 don't need a ticket at Disney World or Disneyland. See more ideas in free things to do with kids.
Frequently asked questions
Do babies fly free?
On U.S. domestic flights, babies under 2 can fly free on a parent's lap with Delta, American, United, Southwest, Alaska and JetBlue. International lap infants usually cost 10% of the adult fare plus taxes, though JetBlue and Southwest charge only taxes and fees.
How old does a baby have to be to fly?
It depends on the airline: American from 2 days, JetBlue from 3 days, United from 7 days and Southwest from 14 days. Delta has no fixed minimum but needs a doctor's letter for babies under 7 days.
Do I need a birth certificate for a lap infant?
Bring proof of age, such as a birth certificate or passport. Southwest requires the original or a photocopy and doesn't accept photos or screenshots on your phone.
Can I bring breast milk or formula through airport security?
Yes. Breast milk, formula and juice are exempt from the 3.4-ounce liquids rule. Remove them from your bag for separate screening. Ice packs are allowed.
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