There's something wacky going on here...
If it was scanned on a Minolta D-S II (I'm not doubting that it was) at the highest resolution, the resulting JPEG should be around 700-800k - I use this scanner too so I should know. Your image is 300,000 odd bytes, so is somewhat compressed. I believe that airliners.net only compresses the image at the same time as the footer with the logo and photographer name is added, so I think it your image is either scanned at a lower resolution than the maximum your scanner will delivery, or has been significantly compressed post scan.
So, a few observations:
* There are some noticeable dirt marks on the image, particularly above the fuselage and APU, and beneath the fuselage just rear of the main gear. A few months ago, you might have gotten away with these but not now - they need to be removed
* Scan at the very highest resolution the Dual Scan II will scan at - 2880dpi. This will produce a huge file which you will need to play with. Reduce the image size to 1024 by whatever using Photoshop after you've cleaned it up after the scan.
* The image link you've posted above shows very noticable JPEG artifacts, especially around the tail. As I said I don;t think airliners.net has introduced these so all I can advise is lay off the sharpen filter.
In terms of scanning, I would recommend you try VueSCan rather than the Minolta software. Out of the box, VueScan has delivered me consistant results without much pain, and I consider the $40 it cost money well spent. Download the trial version and try it yourself.
In the cold light of day, my off-the-cuff thoughts are that the original is probably a bit soft and has been over-sharpened and then saved with some significant JPEG compression. You may regard this as an unfair analysis but I hope I have explained what I think are the problems and why I have arrived at this conclusion.
Despite the glare, if this image is really (honestly) sharp - and you need a loupe to tell, don't just hold the neg/slide up to the light - it might just be salvageable. Good luck.
There are old pilots and there are bold pilots, but there are no old bold pilots