How do I create a View filter by a parent taxonomy term?
Please follow such steps for getting your result (Child Items)  

1)Add Taxonomy term: Term ID in CONTEXTUAL FILTERS.
2)Add Taxonomy term: Parent term in RELATIONSHIPS. (leave Require this relationship unchecked.)
3)Add Taxonomy term: Parent term in filter section. select great than 0.
4)Do not forget to filter your taxnonmy term in mycase Taxonomy vocabulary: Machine name (= airports).
5)Add Taxonomy term: Rendered Taxonomy term to your fields , select relationship to parent , check the Exclude from display.
6)In setting, under FORMAT section. In grouping field 1, select (Parent) Taxonomy term: Rendered Taxonomy term.  

You should good to go. you can use view tpl to add more class base on the group.
 I have enclose my screenshot for references.