Blackburn Blackburn supplied visual early warning

What was the first aircraft to perform an AWACS-like role?

The Blackburn Blackburn was an early equivalent, using airborne observers with binoculars rather than radar to spot threats.

The Blackburn Blackburn was the first aircraft to perform an AWACS-like role, although it carried no radar. Its observers used height and binoculars to extend the fleet's visual warning horizon. The aircraft performed its command-and-warning role through visual observation. This example separates that role from the later sensor technology most closely associated with it.