Aviatter

It is, quite simply, the go-to app for plane spotter enthusiasts!

Plane spotting is a popular hobby, as it’s a lot of fun. Some people take it quite seriously (and so should you!).
Aviatter lets you track your aircraft sightings, see what other people are spotting and help you look up aircraft information.

Features include:
+ Latest Sightings posted by enthusiasts.
+ Customize the sightings feed by keyword or distance from you.
+ Search the sightings to see where your favorite aircraft was spotted.
+ Use the map or your current location for the sighting, or use an undisclosed location for those sensitive sightings.
+ Link to an aircraft with it's registration.
+ Look up aircraft to see it's detailed information.
+ Submit new aircraft or changes to aircraft information in our database.
+ Submit cover photo suggestions for aircraft.
+ Submit aircraft privacy requests for those sensitive aircraft.
+ Look up your friends and see their sightings.
+ View and search your own sightings.
+ Supports dark mode.

It's like social networking for aviation enthusiasts!