Yes, a parent can travel alone with his/her child. To avoid delays or being refused entry or exit at the border, it’s safest to have a travel consent letter signed by the other parent.
You should check your agreement or court order to see if you need the other parent’s permission and if you need to provide the other parent with information about your travel plans, such as your flight details and emergency contact numbers.
Courts will usually allow travel unless they believe that the child is in risk of harm.