These shots makes it clear why you have a hard time grabbing focus on in-flight photographs.
A Great Blue when fully extended is thin, really not much to them at all. Almost as tall as a person, but all feathers and bone. In general not much to focus on when one zooms on by.
If this is what you want to capture…gear counts. Not the brand, old model / new model, or the mirror/mirrorless argument, only a cameras focus points and methods.
I had this conversation with a friend, she rented gear before a purchase. I like that idea.
Most brands can provide what a person is comfortable with, just takes a little homework.
Taken at ACE Basin, South Carolina.
Note; we are Canon users for this type of photography. Ellen is Sony for landscape.