the headlamp adjustment feature is vacuum-controlled. If you have Euro-lamps, and you open up the back of the unit, you will see a small diaphragm (like a small brake booster) that adjusts the aim of the headlamps. If you follow the connections, you will find a vacuum connector on the back of the headlamp unit that this diaphragm is connected to.

i do not have the headlamp adjustment feature on my dashboard, so my headlamp vacuum connector is not connected anywhere.

i can imagine though that if the ambient air pressure drops sufficiently, my headlamps' aim will be adjusted (!)