From the Inventor and the Pilot Russell and Sigurd Varian

Sig was intensely interested in ways to make flying safer and talked about the problems they encountered with inadequate instruments. The pilots lacked instruments that could locate mountains hidden by clouds where Mexican maps indicated swamps, detect planes approaching in overcast or at night, or guide a plane to a safe landing when visibility was obscured. These and many other navigation aids were badly needed, Since this was a subject Sig knew well, he could foresee a promising future for them if they were able to develop instruments of this kind.