c2

Here is a photo of the same passengers inside Air Ferries' Loening C-2H Air Yacht, N58K (c/n 243):

Atlantic (Fokker) C-2A, United States Army Air Corps (USAAC) Serial No. 28-120, "Question Mark". See: en.wikipedia.org/wiki/Question_Mark_(aircraft)

Distinguished aviator (then-) Lieutenant Albert F. Hegenberger (US Army Air Corps) aboard the aircraft "Bird of Paradise," an Army Air Corps Atlantic-Fokker C-2 (itself derived from the Fokker F.VIIa/3m tri-motor airliner) (AAC Ser. No. A.C. 26-202) modified for long distance flight. The instrument just next to Hegenberger's left knee is an aperiodic compass (a.k.a. "deadbeat compass"), a compass which did not oscillate as an aircraft changed headings or was affected by turbulence.

Hegenberger and Lt. Lester J. Maitland (US Army Air Corps) would complete the first non-stop flight from the mainland United States (Oakland, CA) to Hawaii (Wheeler Field, Oahu) aboard "Bird of Paradise," from June 28–29, 1927.

A bit odd to come across this photo (and the photo below) in this most recent posted collection of circa-1921 Bain photos, though Hegenberger was involved with developing navigation instruments and techniques for the Air Service at that time. The "Bird of Paradise" wouldn't be procured until the 1926 Fiscal Year.

See also:
en.wikipedia.org/wiki/Albert_Francis_Hegenberger
en.wikipedia.org/wiki/Bird_of_Paradise_(aircraft)
Here's a photo from the San Diego Air Space Museum's (SDASM) collection on the Flickr Commons of Hegenberger (L) and Maitland (R) next to the aircraft: