Got bad news for you... A homebrew an aviation band transmitter is
illegal.

Bull$#!t.


And also you have to be a pilot or air traffic controller to operate an
aviation band transmitter

Bull$#!t.


- such transmitter must also pass specified
standards to be legal for use.

True.



A reciever is a different matter of course.
There are quite a few manufacturers that make aviation band reciever kits.

Learn to spell receiver.

Jim