You might want to review the following:
https://www.delta.com/us/en/children.../infant-travelI
Infant-in-Arms or Ticketed
When you travel with a child under 2 years old, you may choose to travel with the child on your lap (infant-in-arms) or travel with your child in an FAA-approved child safety seat. To use a FAA-approved safety seat, you must purchase a ticket for your child so they have a reserved seat.
Where to Sit with a Child Safety SeatThe window seat is the preferred location for an approved child safety seat (child restraint system or car seat). Other locations may be acceptable provided the seat is not installed between other passengers and the aisle. An accompanying adult must sit next to the child. More than one car seat may be in use in the same row and section of seats. Per FAA regulations, children under 2 years of age are not allowed to sit in a seat equipped with an airbag seat belt.
When using a child safety seat,
don’t select seats in the following areas:
- Aisle seats
- Emergency exit rows
- Any seat one row forward or one row back from an emergency exit row
- Bulkhead seats when the safety seat is a combination car seat and stroller
- Flatbed seats in the Delta One™ area of the following aircraft: Airbus A330-200 or A330-300; Boeing 777, 767 or 747 aircraft*
*Child Safety Seats are not permitted in this area since the airbag seat belt cannot be deactivated.