Children under 18 may need a Letter of Consent to travel internationally without both parents. Country-specific regulations.A notarized letter of consent is a crucial requirement when traveling with minors without both parents or guardians. See what documents a child needs to travel to or from the US alone or with a parent or relative. Non-US citizen children traveling to the US. One form is an authorization to travel with the child. Minor travel consent form giving partental authorization for child to travel with another person or only one parent. The intention of this letter is to provide consent for a minor child to travel without the company of both legal parents. My ex won't give travel consent form. I have the passport already.