Seriously, there is no restiction that I know of if you are on public property (or your own property) and take pictures of things in plain view.
Sorry but you are very much mistaken. There are signs on most military bases that prohibit photographing or even drawing pictures of the installation without written permission from the commanding General. Even National Parks place certain restrictions on photography.
The signs say certain areas require prior permission and some areas are prohibited for taking photos, but blanket prohibition is simply not there—especially when we are talking about plane spotters off-field taking pictures.