Updated Updated August 28, 2026
Quick answer: babies under 2 fly free as lap children on Southwest domestic flights (taxes and fees apply internationally). You’ll need a birth certificate or passport for age verification, and you can add your baby to an existing reservation online, by phone, or at the airport. Car seats and strollers gate-check for free. Full details, step by step, below.
Table of Contents
- Does Your Baby Fly Free on Southwest? Lap Infant Rules Explained
- How to Add an Infant to an Existing Southwest Reservation
- What Is a Boarding Verification Document?
- Lap Child vs. Buying a Seat
- Do 2-Year-Olds Fly Free on Southwest?
- Car Seats on Southwest
- Strollers on Southwest
- Flying Southwest Alone With a Baby
- What to Actually Pack
- Documents You Need
Does Your Baby Fly Free on Southwest? Lap Infant Rules Explained
Yes, your baby can fly free on Southwest as a lap child, as long as they are at least 14 days old and under 2 years old for the entire trip. A lap child is a baby who doesn’t get their own seat and instead travels on the lap of an accompanying passenger who is at least 12 years old. This applies to domestic flights only. On international routes, you will still pay the government taxes and fees on the adult fare, even though there is no seat cost.
This age window matters more than most parents realize. Southwest is strict about it: the “under 2” rule applies for the entire duration of the trip, not just at booking. If your baby turns 2 between the moment you book and the moment you fly, even by a single day, you will need to purchase a separate seat for them before departure.
What Counts as Proof of Age?
Southwest requires a government-issued document as evidence that your child qualifies for the lap child rate. Accepted documents are a passport, a birth certificate, or a government-issued photo ID. Screenshots, photos on your phone, or immunization records are not accepted, so bring the physical original or a photocopy.
Lap Child or Purchased Seat: The Free Option Isn’t Always the Best One
Flying free is tempting, especially on a budget, but a lap child does not get their own seat, their own safety restraint, or (in most cases) their own carry-on allowance. If you want to use an FAA-approved car seat onboard, which is genuinely the safer option for a baby, you will need to purchase a seat regardless of age. We break down that trade-off in detail further down in this guide.
Quick answer for the impatient parent: under 2 years old, on your lap, free on domestic flights, taxes and fees only on international flights. Bring a birth certificate or passport. That’s the rule in one sentence.
How to Add an Infant to an Existing Southwest Reservation (Step by Step)
If you booked your flight before your baby arrived, or simply forgot to add them, you can add a lap infant to an existing Southwest reservation at any point before departure, even at the airport on the day of the flight. Southwest’s own Help Center barely explains this, so here is the actual walkthrough.
Adding a lap infant does not require a new ticket purchase for domestic flights. It simply updates your existing reservation record so the airline knows a child under 2 years old will be on your lap.
Option 1: Online Through Manage Reservations
- Go to Southwest.com and log in, or have your confirmation number and the traveler’s last name ready.
- Open Manage Reservations and pull up your existing trip.
- On the passenger step, look for the option to add a lap infant and enter your baby’s full name and date of birth.
- Confirm the update. For domestic flights, there is no additional fee to pay at this stage.
Option 2: By Phone
Call Southwest Reservations at 1-800-I-FLY-SWA (1-800-435-9792). This is the airline’s real customer service line, not the confirmation number Southwest generated for your booking. Have your confirmation number and your baby’s date of birth ready. This is also your best option if you’re adding an infant to an international itinerary, since taxes and fees will need to be calculated and added to your reservation.
Option 3: At the Airport
If you land at the airport without having added your infant online or by phone, you can still do it at the self-service kiosk or at the ticket counter on the day of travel. You will need to show your proof of age document (birth certificate, passport, or government-issued photo ID) at this point, since the agent will verify it before issuing your Boarding Verification Document, which we explain in the next section.
Real talk: don’t leave it to the last minute if you can help it. Adding your lap infant online during booking or shortly after takes two minutes. Doing it at a crowded airport counter with a fussy baby on your hip is a very different experience.
What Is a Boarding Verification Document, and Do You Actually Need One?
A Boarding Verification Document, often shortened to BVD, is the closest thing your lap infant will get to a boarding pass. It’s a printed slip confirming your baby’s age has been checked by a Southwest agent, and you’ll be asked to show it at the security checkpoint and again when you board. Your baby doesn’t get an actual boarding pass, since they’re not occupying a seat, but Southwest still needs a way to confirm at security and at the gate that your child has been age verified and is legitimately traveling as a lap child.
When and Where You’ll Actually Get It
Here’s the part most guides skip: in practice, Southwest typically issues the BVD when you check in at the airport, whether that’s at the self-service kiosk or the ticket counter, not in advance online. Even if you already added your lap infant to your reservation days or weeks before your flight, plan to arrive with enough time to check in at the counter and pick up the document before heading to security.
Where you can get your BVD:
- At the self-service kiosk, if your lap child is already on the reservation
- At the ticket counter, where an agent will check your proof of age document
- Occasionally by phone in advance, though this is inconsistent and you should not count on it
What to Bring So You Actually Get It Without a Hassle
Have your baby’s birth certificate, passport, or government-issued photo ID ready. The agent needs the original or a physical photocopy, not a photo on your phone. Once verified, you’ll get a printed BVD that you carry alongside your own boarding pass through security and onto the plane.
Good to know: the BVD is not the same as enrolling your baby in Rapid Rewards. Some parents do both, since a Rapid Rewards profile with a verified age on file can occasionally make future check-ins smoother, but it’s not required to fly.
Lap Child vs. Buying a Seat: A Straight Answer for Southwest Flights
There’s no universally right answer here, it depends on your flight length, your budget, and how confident you feel holding a squirming baby for hours. Choosing a lap child means free travel on domestic Southwest flights but no dedicated seat or restraint system. Choosing a purchased seat means paying full or discounted fare, but you can bring an FAA-approved car seat onboard. Here’s the honest breakdown, without the fear-mongering some guides lean on.
| Lap Child | Purchased Seat | |
|---|---|---|
| Cost | Free on domestic flights, taxes and fees only on international flights | Full or discounted fare, depending on the route |
| Safety | No dedicated restraint; you hold your baby throughout the flight, including turbulence | FAA-approved car seat secures your baby in their own seat |
| Comfort on long flights | Gets harder as flight time increases; your arms and lap do all the work | Baby has their own space to sleep or sit, which can mean more rest for both of you |
| Car seat handling | Car seat must be gate-checked or checked as luggage | Car seat travels in the cabin, installed in your baby’s own seat |
| Best for | Short flights, tight budgets, babies who nap easily on you | Long flights, parents flying solo, babies who sleep better in their own space |
My honest take: for flights under two hours, I’ve made the lap child option work just fine. For anything longer, or if I’m flying solo, the peace of mind of a properly installed car seat is worth the extra cost to me. Neither choice is wrong, and flying is statistically far safer than driving with your baby either way.
Do 2-Year-Olds Fly Free on Southwest? The Age Rule Nobody Explains Clearly
No, once your child turns 2 years old, they no longer qualify as a lap child and must have their own purchased seat, even for domestic flights. The rule that matters is your child’s age on the day of travel, not their age when you booked the ticket, and it applies for the entire duration of your trip, including the return flight.
The Round-Trip Birthday Trap
This is the scenario that catches families off guard the most. If your trip spans your child’s second birthday, the return leg requires a purchased seat, even though the outbound leg was free. Plan ahead, and book that return seat in advance rather than dealing with it at the airport.
Do You Actually Get Checked?
In practice, many parents report that gate agents rarely scrutinize a child who looks close to the age cutoff. That said, relying on not getting checked is a gamble, not a strategy. If your child has genuinely turned 2, purchase the seat. It’s the safer and more honest choice, and if you get flagged without a ticket, you may be asked to buy one on the spot at a less favorable fare.
Practical tip: if your child’s second birthday falls within a few weeks of your travel dates, call Southwest directly to check how they want the reservation handled. It’s a five-minute call that saves you a stressful conversation at the gate.
Car Seats on Southwest: FAA Approval, Gate-Checking, and Seat Selection
Southwest allows FAA-approved car seats onboard, but only in a window seat, never in an aisle or exit row. An FAA-approved car seat is a Child Restraint System carrying a label confirming it meets federal aviation safety standards, and not every car seat that’s safe for your actual car is automatically approved for use on a plane, so check the label before you fly.
Since January 2026: Southwest moved to assigned seating. This is no longer something you sort out after boarding, you need to book or select that window seat in advance, because there’s no more grabbing an open seat once you’re on the plane.
Required if you want to use the car seat onboard. A lap child has no seat to install it in.
Select it at booking if your fare allows it. On Basic fares, check in as early as possible.
Not buying a seat? Gate-check or counter-check the car seat, one per child, no charge.
Practical tip: gate-checking means you drop the car seat right at the jet bridge before boarding and pick it up in the same spot when you land, instead of waiting at baggage claim. It’s the easiest option if you plan to use the car seat again shortly after landing, for example in a rental car or taxi.
Strollers on Southwest: What Counts as Carry-On vs. Gate-Check
Southwest does not allow strollers in the cabin, no matter how compact or umbrella-style they are. Every stroller gets gate-checked or checked at the counter, but the good news is it’s completely free, one per child, separate from your regular baggage allowance.
Drop the stroller when you check your bags. You won’t see it again until baggage claim at your destination.
Keep the stroller through the terminal and security, hand it off at the jet bridge, get it back in the same spot on landing.
For most parents, gate-checking is the better option. You get to use the stroller for the entire walk through the airport, which is often when you need it most, and you get it back immediately on arrival instead of waiting at baggage claim with a tired baby.
Any Type of Stroller Is Accepted
Whether you’re traveling with a lightweight umbrella stroller, a full-size travel system, or a jogging stroller, Southwest accepts it under the same free stroller allowance. There is no size restriction specific to strollers the way there is for regular carry-on bags.
One thing worth knowing before you go: Southwest’s own policy states it will not assume liability for damage to strollers or car seats checked this way. If you’re traveling with a stroller you’d hate to see damaged, a protective travel bag for it is a cheap way to add peace of mind.
What About a Wagon?
Wagons follow a similar logic to strollers when it comes to gate-checking, though they’re bulkier and less universally accommodated than a standard stroller. If you’re planning to bring one, it’s worth calling Southwest ahead of your flight to confirm it will be accepted at your specific airport.
Flying Southwest Alone With a Baby: A Solo Parent’s Real Playbook
Every guide I’ve read assumes there are two adults, one holding the baby while the other handles bags, the stroller, and boarding passes. As a solo mom, I don’t get that luxury, and neither do a lot of parents. Here’s what actually works when it’s just you and your baby against the airport.
A soft carrier frees both your hands for bins, your bag, and the stroller fold. You can keep baby in the carrier through the checkpoint in most cases, just ask the TSA officer.
Keep the stroller with you as long as possible. You need it to move through the terminal, and you get it back the moment you land instead of waiting at baggage claim.
You don’t need extra stress on top of managing a baby alone. Arriving with buffer time means you’re not rushing to fold a stroller one-handed while someone waits behind you.
Gate agents and flight attendants deal with solo parents constantly. Asking someone to hold your boarding pass or watch your bag for thirty seconds is completely reasonable.
From my own experience: the hardest part usually isn’t the flight itself, it’s the logistics right after landing, managing an uneven jet bridge or tarmac with a suitcase, a stroller, and a baby all at once. Give yourself extra time on arrival too, not just at departure.
What to Actually Pack: A Baby Flight Checklist That Isn’t Generic
Skip the generic “bring diapers and snacks” advice. Here’s what actually matters, organized by where it needs to be during your trip.
Carry-On (Your Personal Item or Bag)
Gate-Checked
Easy to Forget
Formula, breast milk, and baby food are exempt from the standard TSA liquid limit, but declare them separately at the security checkpoint so they don’t get flagged.
Documents You Need: Birth Certificates, IDs, and Passports
For domestic Southwest flights, your baby doesn’t need a passport, but you do need proof of age for the lap child rate.
| Document | Accepted? |
|---|---|
| Birth certificate (original or photocopy) | Yes |
| Passport | Yes |
| Government-issued photo ID | Yes |
| Screenshot or phone photo of any document | No |
| Immunization records | No |
International Flights
If you’re flying internationally with Southwest, your baby will need a valid passport, even as a lap infant, since the lap infant fare still requires a ticket at a reduced cost covering taxes and fees.
Don’t have a birth certificate handy yet? Call Southwest in advance if you need to travel before you’ve received the physical copy. They can advise on alternative verification for your specific situation.
Frequently Asked Questions
Do babies fly free on Southwest Airlines?
Yes, babies under 2 years old fly free as lap children on Southwest domestic flights. International flights require taxes and fees on a reduced infant fare.
Do 2-year-olds fly free on Southwest?
No. Once a child turns 2, even on the day of travel, they need their own purchased seat and can no longer travel as a lap child.
How do I add an infant to my Southwest flight?
You can add a lap infant online through Manage Reservations, by calling Southwest at 1-800-435-9792, or at the airport kiosk or ticket counter on the day of travel.
What is a boarding verification document on Southwest?
It’s a printed document that confirms your lap child’s age has been verified. It functions like a boarding pass and is typically issued at the airport at check-in.
Is a car seat considered a carry-on or checked bag on Southwest?
Neither, in the usual sense. A car seat is allowed onboard for free in a purchased window seat, or checked for free at the counter or gate if not used onboard, separate from your regular baggage allowance.
Does a stroller count as a carry-on on Southwest?
No. Strollers are never brought into the cabin on Southwest. They’re gate-checked or checked at the counter for free, one per child.
Can you gate-check a stroller and a car seat at the same time?
Yes. Southwest allows one stroller and one car seat per child to be gate-checked or counter-checked for free, and you can do both on the same trip.
How old can a lap child be on a Southwest flight?
A lap child must be at least 14 days old and under 2 years old for the entire duration of the trip.
Does an infant need an ID or passport to fly domestically?
Not a passport. For domestic flights, a birth certificate, passport, or government-issued photo ID is accepted as proof of age for a lap child.
What documents do you need to fly with a baby on Southwest?
Bring a birth certificate, passport, or government-issued photo ID as an original or physical photocopy. Digital screenshots and immunization records are not accepted.
“Southwest makes flying with a baby genuinely manageable, free lap child travel, generous gate-checking, and a boarding verification process that, once you know it, takes five extra minutes at most.”
The real key is knowing what to expect before you get to the airport: bring the right documents, book your seat early if you want a car seat onboard, and don’t count on the old open-seating shortcuts that no longer exist. Do that, and Southwest remains one of the easiest US airlines to fly with a baby.
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