An aircraft operation used for specialized services such as agriculture and observation is called?

The term that accurately describes aircraft operations used for specialized services such as agriculture and observation is "Aerial Work." This classification encompasses various activities where aircraft are utilized for purposes other than passenger transport or freight, focusing instead on specific tasks such as agricultural spraying, aerial photography, surveying, and search and rescue operations.

Aerial work stands apart from general aviation, which broadly includes all flights other than military and scheduled airline flights, and does not focus on specialized tasks. While "Special Purpose Aviation" might seem relevant, it is not a standard term widely recognized in aviation literature for categorizing these operations. Lastly, "General Purpose Operations" suggests a broader or more casual use of aircraft that doesn't specifically address the tailored nature of tasks performed in aerial work. Hence, "Aerial Work" is the most accurate descriptor for such operations.