Under 5: Children cannot travel alone.

Airtran: Children 5 to 11 years of age will be accepted only on nonstop or direct flights (flights with one stop but no change of planes) between their origin and destination.

American Airlines: Children 5 to 11 years of age will be accepted only on nonstop or direct flights between their origin and destination.

Delta: Children 5 to 7 can travel on non-stop flights only. Children 8 to 14 may travel on nonstop and direct flights only.

Jet Blue: Children 5 to 14 may travel unaccompanied on nonstop flights.

Southwest: Children 5 to 11 years of age will be accepted only on nonstop or direct flights between their origin and destination.

Spirit Airlines: Children 5 to 14 may travel unaccompanied on nonstop flights.

United: Children 5 to 11 years of age will be accepted only on nonstop or direct flights between their origin and destination.

US Airways: Children 5 to 14 may travel unaccompanied on nonstop flights.

Virgin America: Children 5 to 14 may travel unaccompanied on nonstop flights only.

For tips for flying with kids, read our latest article here.