Since the DOSBox prefetch behaviour is Pentium-style, some old demos don't work anymore. Flight is one of those. The source of the workaround is a bit long to post, so if anyone is interested, it's available from my site (pferrie.tripod.com).
by "don't work any more" do you mean they worked in dosbox somewhen?
Qbix doesn't like my prefetch stuff (which is pretty short in fact) so it was
never committed
That would be "don't work in DOSBox, or on any modern machine". The problem with enabling the 486 behaviour is that some other demos (and other applications) rely on the Pentium behaviour. You'd need a switch (might be slow) or a separate compilation (inconvenient). Or I make more patches. :-)
Switch isn't slow as it's basically an additional core.
I've got this to work using prefetch queue emulation. The demo doesn't
run though as it accesses some floppy disk (which your fix removes).
Any idea why they need a (any?) floppy?
Maybe - according to some messages in the code (once it's fully decrypted), the protection had the option of using a key file that existed on a floppy. The demo doesn't use the file, it just checks for the existence of the drive. If you pretend that the drive is there, then the demo should run.