How to Open Mac OSX Lion on High Sierra

As I wrote "...that installer can only be used on Macs that are not compatible with later operating systems. Your 2011 MacBook Air doesn't qualify since it is compatible with the operating system it's running (High Sierra)."

The short answer is yes, but we cannot install any operating system on a Mac that is already running a more recent one. This has always been the case.

The solution is to erase the Mac first, leaving it with no operating system. Obviously you will want a contingency plan in case things don't work out for a variety of reasons.

As D.I. Johnson wrote more information would help.

DominikBailey wrote:

i dont want to erase my mac, just install the operating system on my usb drive

As I wrote we cannot install an operating system on any Mac that is already running a more recent one, and if that USB flash drive is plugged into a Mac running High Sierra, then that Mac is running a more recent operating system.

Edited after posting: I am not sure we can create a "bootable installer" for Lion. The createinstallmedia command may not have been available until later. For the time being I can suggest this: Mac OS X Lion Installer - Apple Support, but as it states that installer can only be used on Macs that are not compatible with later operating systems. Your 2011 MacBook Air doesn't qualify since it is compatible with the operating system it's running (High Sierra).

Yes. The 2011 MBA originally shipped with OS X Lion, so it should have no problem opening the Lion installer.

Are you having some problem?

If you elaborate, perhaps someone here can offer guidance.