I've recently uncovered the original cassette "Master Maker" disk for Skyway. This is the program that creates the cassette master, along with custom loader, to be sent off to the duplicators.
The Master Maker produces a cassette with a custom loader that creates the loading screen in a top-down fashion, filling in the colours as it goes. It also loads at a higher speed and gives the time until completion.
Skyway was never completely finished (see Skyway) but as cassette demo's were sent out to various companies, I needed to get the game onto cassette and get it to look as much like a finished product as possible. Custom loaders were common at the time, and I figured that if it looks good on loading, then I've already set a positive expectation. Well, that was my theory.
The reason the loading screen in the first image looks a jumble is because the bytes of the loading screen have been reordered into a left-right, top-bottom arrangement, so they are in the correct order when the cusom loader places them on the screen. This results in the third image. To see what I mean, download the TZX file from here, load it into your emulator and watch.
The MGT +D disk image suitable for loading into an emulator or raw writing to 3.5inch DD floppy, can be downloaded from this website: Skyway Cassette Master Maker +D Disk (gzipped)