Can anyone describe a situation where something viewed from an aircraft may not be permissible under the plain view doctrine?

What is considered curtilage? What if my neighbors that live behind me can look out their upstairs window and view into my backyard, do I still maintain a reasonable expectation of privacy in this area? While backyards have repeatedly been held to be curtilage and therefore protected from warrantless searches under the Fourth Amendment, what about the neighbors. Should they be considered the public and therefore my expectation of privacy diminished?