There is no official airline or safety rule stating that the youngest child must sit in the middle seat, but it is a very common "family strategy" for both logistical and safety reasons. Placing a child in the middle seat between two adults (usually parents) provides a "buffer zone" that prevents the child from reaching into the aisle or bothering a stranger in the window seat. It also makes it easier for both parents to assist with snacks, entertainment, and seatbelts. From a safety perspective, the FAA and CAA recommend that car seats (CRS) be placed in the window seat so they don't block the exit path for other passengers in the row; if you have two children, one would typically be in the window and the other in the middle. If a child is small enough to be a "lap infant" (under 2), they don't have a seat at all. In 2026, many families use "Family Boarding" to ensure they can secure a full row, placing the youngest in the middle to keep them contained and supervised by an adult on either side throughout the flight.