I visited another airmail navigation arrow located beside I-15. This one is off the Halloran Summit exit, 15 miles north of Baker, CA. The arrow is atop a lava rock butte and is at the end of a 4wd trail that's visible in Google satellite imagery. Here's a Google map centered on the arrow. You can either hike to the arrow or drive a 2 mile 4wd trail. The arrow is located at the green circle on the photo below.
The first mile of trail, up the wash, is mostly easy. It's brushy in places and sometimes narrow. Even with a bit of "trail maintenance", there was a lot of creosote scratching against my car's body panels and I'm sure I'll need to buff out some of them.
I decided to hike the last mile to the arrow. The trail turns up onto the butte and becomes more rugged. It would take me less time the walk, since I'd be driving that section very slowly. I've driven 4wd trails in this area and the lava rocks can be brutal on your tires. In hindsight, I should have driven it. The difficult part is only about 60 yards long.
The arrow appears to pointing toward Mountain Pass.
I don't know if this is the original structure.
The adjacent peak has a curious cross lying on it. I might return to investigate that.