As the NOA_double reason seems to be one of the most discussed we started to redefine it. Yes we know it's still not perfect, but see it please as a first step.
The reject reasons can be found here:
the one we are talking about is here
For your convenience here is the complete text with the changes outlined in red.
You already have photos of this aircraft in the Airliners.Net database that are the same as or very similar to these photo(s).
In order to receive this rejection, the other (similar) photos in the database must also have been taken by you, at the same day and at the same airport. Please do not upload multiple sequential shots of an aircraft during landing, taxiing or take-off, taken only a few seconds apart. Eventhough these photos may appear to be from different angles, we consider them similar. Please select the best shot from the sequence and upload only that one. One shot taken during landing, and another during take-off will generally NOT be considered a DOUBLE error.
In certain cases you can also get this rejection if there are photos in the database that are nearly identical to the one(s) rejected here, but taken on another date by you. Examples of this are photos of stored or preserved aircraft that have not moved since you took the other photos.
For window views we accept 2 shots per flight and side of aircraft when they show considerable different motives. So in other words the maximum number of accepted window views of the same registration on the same flight all taken by you would be 4.
For cabin views we allow 2 shots per registration, date and photographer, when they show considerable different motives. The same applies for cockpit views.
Note: This situation will also occur if there are other photos very similar to these that are still in the upload queue and are waiting for the final screening.
We truly hope this helps.