You are referencing a previous DevBlog. Currently players can "pre-drop" to send home the attacking flight of planes. Holding down the F key would provide a similar function.
The prior Devblog mentioned shooting down planes that were not at the "end" of the squadron. Those holes would remain unfilled and could affect attacks by making an attack which is less-then-whole. If a player had multiple attacks worth of planes, but wanted to send back a section that was not whole, they could hold the F key to do so (rather than attacking the water as is currently normal when "pre-dropping").