If you are traveling with twins — or two children both under 2 — you may have assumed you can sit together as a family of four across one row. Most U.S. and international carriers will not permit it, and the reason is a specific safety regulation you need to understand before booking.
The One Extra Oxygen Mask Per Row Rule
Aircraft oxygen systems are designed so that each row has one extra drop-down mask beyond the number of seats. That spare mask exists for a lap infant held by a seated adult. Because only one spare mask exists per row, a second lap infant in the same row would have no supplemental oxygen in a decompression event. The FAA does not explicitly codify this as a named rule, but all major U.S. carriers interpret the oxygen-equipment requirement (14 CFR Part 121) to prohibit two lap infants in one row. International carriers follow ICAO guidance that reaches the same conclusion.
What This Means for Seating Two Babies
Two adults each holding a lap infant must sit in different rows. On a standard 3-3 aircraft, the closest configuration is rows 15A and 15D — same physical row number but different row segments counts in some crew systems. Most gate agents interpret "row" as the physical row, meaning both infants must be in genuinely different numbered rows. You will need to book seats in adjacent rows, not side by side.
The Practical Workaround for Large Families
The safest solution for families with two lap infants is to purchase an FAA-approved car seat and buy a seat for at least one child. The FAA strongly recommends a purchased seat with a car seat for all children under 40 lbs regardless — this also eliminates the oxygen-mask constraint entirely for that child. For twins, buying one seat and using one lap-infant ticket keeps you compliant and together in adjacent rows, with the car-seat child next to a parent and the lap infant one row away.
How to Verify Before You Fly
Call the airline after booking and ask the reservations agent to note in your record that you have a lap infant. If you have two, explicitly ask how they handle two lap infants and confirm in writing (email the transcript or agent notes reference number). Gate surprises on this rule can result in one adult being moved to an entirely different cabin section.
