With migration in full swing, here's an eBird option that may unknown to some. Seasoned eBirders will already be aware of the "Flyover" option under "Breeding Codes", but newer eBirders that missed the rollout at its inception may not be aware of this selection that lies buried at the bottom of the "Breeding Codes" list. "Flyover" is a selection created for birders who want to specify birds that are observed overhead, and was added to eBird later in the game so that's probably why a non-breeding behavior is lumped onto the pre-existing "Breeding Codes" list. (When eBirders use presets from the "Breeding Code" list, those factors can then be filtered by researchers doing advanced searches on checklists.) Be aware the "Flyover" option applies to a limited category of birds in the sky - here's a brief description from eBird:
When to use the Flyover code
Please use "F" to indicate cases in which flying birds are not interacting with the habitat below; "F" should not be used if birds appear to be foraging as they fly or potentially searching for food or sites at which to land in the habitat immediately below. Obviously some birds may fly overhead while moving from one tree to another or briefly flushing, circling, and dropping back in to a puddle. These examples are not the intended use of "F".