United allows travellers under the age of 18 to travel alone without any parent or guardian only if they have applied for United Airlines Minor Travel PolicyUnited Airlines Minor Travel Policy which is made for extra safety and special services for kids such as pre-boarding, snacks during the journey, and so forth. However, this policy would not be functional for any connecting flight. Kids younger than 5 can't go as unaccompanied minors regardless of whether they are flying with the qualified unaccompanied minor youngster.