Photo © Felipe Escalona
Photo © Jay Davis
I highly doubt its just a coincidence.
What other airline liveries do you know of that are quite similar?
The first one is Allegheny Airlines, before they became USAir.
The second one is Central Airlines, a feeder airline that was merged into Frontier in 1967.
Different colors, but the shape and design was pretty similar.
There's a better picture of the Central Airlines logo on this website:
I'd post the link to the .jpg file but it's on a tripod site and tripod fixed it where you can't link photos to external sites. But go to the above site and scroll down to the 4th image.
BTW, the first image on the above page shows how Central's final livery would have looked on some DC-9's they had ordered. Unfortunately, Frontier merged with Central before the planes were actually delivered and they never flew with that livery.
... but Western's logo was at the front of the cheatline and smaller.
This 1964 time table shows Mohawk's indian logo better.
And this website with old Western Airlines memorabilia shows Western's Indian ogo.