Can't install Mavericks to virtual machine

vmaurice wrote:

There is a Macbook Air mid-2011 in another location that I want to upgrade to High Sierra. The installer refuses, saying the machine first needs to be upgraded to Mavericks.

That probably means "Mavericks or better."

My suggestion would be to try to upgrade that MacBook Air to El Capitan or Sierra, and from there to High Sierra.

If the ancient version of macOS on that MacBook Air isn't able to handle the https security on this Apple Support article, you could use a modern Mac or PC to download the .DMG installer for El Capitan or Sierra and put it on a USB drive for transfer to the old Mac. This would not create a bootable installer – you would still need a working copy of Mac OS X on the old Mac to open (mount) the .DMG and run the installer inside. But it would be a way of working around a "this version of Safari is too old to access the Support article" problem.

How to download and install macOS - Apple Support

Parallels only supports Mavericks if it is on a Mac that Mavericks is supported as the host operating system. Apple does not presently provide any version of Mavericks for download.