The problem is that WinImage is not just a disk writer, but also a file extractor. So it always insists on trying to process the file system within the disk image. It only knows about FAT file systems, and it is too stupid to know about DOS 1.x disks which lack or have an incorrect Bios Parameter Block in the boot sector. Many game "booters", such as flight simulator, don't even HAVE a file system!
At any rate, there is not much you can do about it other than use a different disk writer tool.
If you are using a computer with a real Floppy Disk Controller and not a lobotomized USB floppy drive, then the best options are DOS based disk writers.
You can write "raw" 160K/180K/320K/360K disk sector images (.IMG, .IMA) with M Brutman's DSKIMAGE tool:
http://www.brutman.com/PCjr/pcjr_downloads.html
And many archives are in ImageDisk (.IMD) format:
http://www.classiccmp.org/dunfield/img/index.htm
There is a guide to convert raw 160K/180K/320K/360K disk sector images to ImageDisk format here:
https://winworldpc.com/winboards/viewtopic.php?t=6931
If you absolutely need a solution for "modern" lobotomized hardware, then you can feed the above IMA,IMG,and IMD files to the HxC disk tool, save them as a SuperCard Pro or KryoFlux stream and write those using one of those devices.
WinImage can create 160kB images
It says it can, but it actually gets it wrong.
Furthermore I currently don't have 160k disks.
160K is Single Sided Double Density in DOS 1.x 8-sector format. You can write these to any Double Sided Double Density 5.25" (360K) media. You can also tell most disk writers to write them to Double Density 3.5" (720K) media.
Also Flight simulator 1.05 only comes in the same format of IMG file and I cannot mount or burn it and most normal programs I use report it as corrupt. How in the world can I get the files out
Flight Simulator doesn't have files.
For others, unless someone has written a smarter file extractor, the only way is to hex edit the image to add a correct Bios Parameter Block.