SIZE
The size of your photo(s) was too small or they had a very unusual width/height ratio.

Images should be at least 1000 pixels wide and at least 667 pixels high for landscape format photos, or 1000 pixels high (the longer side) and 667 wide for portrait format photos.

The following table list the acceptable sizes for photos. You will see that the width/height ratio should be in the region* of 3:2 or 4:3

Landscape photos:

The first number is the longer side (horizontal) * second number is the shorter side (vertical one) in a 3:2 ratio and third (last) number is the shorter (vertical) side in a 4:3 ratio. Note that these numbers do not include the Airliners.net copyright banner which is added during upload, and is 12 pixels high. This would then add 12 pixels to the shorter (vertical) size.

1000 * 667 -> 750
1024 * 683 -> 768
1100 * 733 -> 825
1200 * 800 -> 900
1300 * 866 -> 975
1400 * 933 -> 1050
1500 * 1000 -> 1125
1600 * 1066 -> 1200

Portrait photos

The first number is the shorter side (horizontal) * second number is the longer side (vertical one)** in a 3:2 ratio and third (last) number is the longer (vertical) side in a 4:3 ratio. Note that these numbers do not include the Airliners.net copyright banner which is added during upload and is 12 pixels high. This would then add 12 pixels to the longer (vertical) size.

667 -> 750 *1000
683 -> 768 *1024
733 -> 825 *1100
800 -> 900 *1200
866 -> 975 *1300
933 -> 1050 *1400
1000 -> 1125 *1500
1066 -> 1200 *1600

Photo copyright © Thierry Deutsch	Photo copyright © Paul Markman

Examples of justified and acceptable 4:3 ratio photos

Despite some misunderstandings lately this rule still applies as mentionned above; if justified by some motivational reason an exception may be made. Normally a 3:2 ratio is preferred by A.net so unless you want to include some spectacular background or any other frame-filling detail that justifies a wider crop, try to get as close as possible to the 3:2 ratio.

A.net wants the uploaded pictures to fit in between the 3:2 to 4:3 ratio; mathematically spoken this would mean between 1,5 to 1,333. That means that if you divide the number of pixels from the longer side of your picture by the number of pixels from the shorter side of your picture you have to get a number of 1,333 to 1,5. If the resulting number is smaller than 1,333 or bigger than 1,5 your ratio doesn't match and you're in for a size rejection.

The size tables shown for landscape and portrait format photos show you the minimum and maximum number of pixels allowed on the shorter side of your picture for the respective longer side to match the given ratios. That again means that even though the minimum total number of pixels for each picture is 667 resp. 1000, those minimum numbers increase if you increase the size of one side.

* To avoid unnecessary rejections, translate "in the region of" with "between" and not with "more or less".

** The second number in the shown table is actually the maximum size of the shorter side (horizontal one) corresponding to the respective vertical side.