My just-over-2 year old granddaughter is afraid of aircraft of all kinds passing overhead. No one knows why, and she isn't verbal enough to explain, though she is getting schooled in feeling words. She is fine with flying in jets and does so several times per year. I don't think she's doing it for attention, as she can be completely engrossed (alone or together) in something but looks startled if a plane flies overhead.
Unfortunately for her, there is a small airfield near my neighborhood where pilots (single engine only) often practice takeoffs and landings. One plane can take off and land 20 times a day! This is hard for her, though the planes aren't particularly loud.
I acknowledge her fear, but try to reassure her that there's little to fear by being "friendly" to the pilot (e.g. waving at them) and explaining what's happening (aiming for her level).
I am toying with the idea of taking her to the airfield and letting her see airplanes up close that are not in use, but am afraid it might backfire if a plane starts to taxi on the runway. Has anyone else had a similar experience and found something helpful in dealing with it?