Aircraft registrations can be found in books, with online resources, or in monthly magazines from enthusiast groups. Most spotters maintained books of different aircraft fleets and would underline or check each aircraft seen. Each year, a revised version of the books would be published and the spotter would need to re-underline every aircraft seen. With the development of commercial aircraft databases spotters were finally able to record their sightings in an electronic database and produce reports that emulated the underlined books.
Aircraft registrations can be found in books, with online resources, or in monthly magazines from enthusiast groups Most spotters maintained books of different aircraft fleets and would underline or check each aircraft seen. Each year, a revised version of the books would be published and the spotter would need to re-underline every aircraft seen. With the development of commercial aircraft databases spotters were finally able to record their sightings in an electronic database and produce reports that emulated the underlined books.