Andrei, I just have a couple pieces of advice, which apply to any sort of photography.
First, I think it's not the best idea to just indiscriminately upload everything you have. Pick out your best shots and submit those. A lot of amateur or beginner photographers sort of have a thing where they fall in love with all of their photographs, but really maybe only 10% at most are even worth considering. This is true of all photographers - I know a lot of pros who say when shooting film they're lucky to get one good shot per roll of film. Now, the other 35 or however many shots on that roll may be a lot better than pictures almost anybody else would take, but they have set a standard for themselves and to them, those shots aren't good enough. I think this is the point of it; if you consciously pick out your best pictures, you will continuously raise your own personal bar higher and higher and you will both become a better photographer and also become a more efficient photographer, since you will waste less time on subjects that are not even worth shooting to begin with. Think about taking good photos, not just taking a lot of photos and hoping a few of them make it into the database through sheer numbers.
Second, pay attention to your technical issues, especially in post-processing. Many times you will have a good shot set up and events will just conspire against you; the light goes bad, you've messed up a setting on your camera, or whatever. Some of these things you can't control, and you will have to deal with it in post-processing. Some of these things you can control, though; especially your camera settings. Make sure you're using good ISO ratings for the types of shots you need, the least amount of compression possible, as well as good aperture and shutter settings (if your camera lets you set these). Try using a tripod if you don't already. If you do mess any of these things up, you can try fixing things later, but understand you may not always be able to and you may have to just abandon a shot you really wanted. It happens.
After you've taken your pictures, look at them in an image editor, pick out the best ones and then see if they need any improvement. Some may not, but most will need at least something, whether it's a little bit of unsharp mask, some level adjustment, saturation adjustment, color balancing or whatever. Make sure your photos look the best that they can on a technical level before uploading. Even after you get good at it, you may still find yourself spending 15 minutes or so on each photo. There's no point in rushing it; these are your photos, and you want them to look the best they can.
You say you used a Fuji S5000 camera. I just checked out Steve's Digicams' review of this camera and found this at the end:
"Other cameras give you a choice of both the image size and quality, the S5000 offers only a resolution setting, I prefer being in control of both of these parameters. You can see some compression artifacts in blue-sky areas that could be eliminated with a finer JPEG compression setting."
So there's nothing you can do about this particular issue (which is an issue on many of your photos) on that camera. You may want to upgrade your camera to a newer model that allows you to shoot RAW mode, or at least set your own jpg compression level. In the meantime, though, you can use an application like NeatImage to try to cut down the jpg compression artifacts - NeatImage can be a big help in a case like this.
I do think there are some shots here - especially some of the full-body side shots of aircraft without any obstructions - that might get through if you cleaned up the photos a bit (color balance, compression artifacts, levels, etc.) and then resubmitted. Try it and see what happens. But pick and choose which photos you resubmit, making sure you only select photos similar to others you see on this site (at least until you've got a better idea what the screeners want), and make sure you fix them up so they look the best that they can.
I'm tired of being a wanna-be league bowler. I wanna be a league bowler!