RichinSeattle

It's pretty clear that this a Navy troop ship, carrying USAAF personnel home from the Pacific Theater. As there are a lot of USAAF officers visible, many aboard the ship must be fighter and/or bomber pilots, navigators and/or bombardiers (all officer-only positions). The Naval officer is most likely the ship's captain.

Welcome home gentlemen.

Chout Loc: Central Texas

If I am not mistaken, the questions were 1) the SSI in the first photo and 2) the insignia on the cap of the individual facing the camera in the second photo.
1) The SSI (Shoulder Sleeve Insignia) is that of the Army Air Force worn by most states side personnel. It is sometimes referred to as the Hap Arnold patch. Its position on the left sleeve indicates it is the SSI of current unit of assignment. A SSI on the right sleeve indicates a former wartime assignment, i.e. a combat patch.
2) The service cap insignia is that prescribed for wear by commissioned officer in the United States Army, the displayed eagle from the seal of the US.
The "Crush" on the cap and the fur collared flight jacket would indicate the officer is a pilot or aircrew. Though the rakish appearance of the airman was appropriated by their ground bound support personnel as well. The crush was attained by removing the stiffener from the interior top of the cap to facilitate the wearing of headphones whose continued wear bent the sides down towards the center of the cap.
The quickest way to determine if the naval officer is Navy or Coast Guard would be to see the device centered above the rank stripes on the sleeve.
The officer wearing the overseas/garrison cap is a Lieutenant as indicated by the single bar on his epaulet and on the left side of his overseas cap. Whether he is a Second Lieutenant or a First Lieutenant is hard to discern due to glare reflecting from the metal surfaces. The epaulet looks more silver but the cap appears more gold.
As Imagery Analysis was not my Military Occupational Specialty, I can not be more specific.

jmdenver Loc: Colorado

Well, the fact that the air corp personnel and navy personnel are together in this photo makes sense. My Dad was on an aircraft carrier. So I would think a bunch of these men would be returning home together as they rotated out.

jmdenver Loc: Colorado

Thanks for this explanation, Chout. It's still interesting what one can discern from a 75 year old kodachrome slide.

LFingar Loc: Claverack, NY

The ship is obviously coming into port. The captain will be on the bridge, not on deck mingling with passengers.

b top gun

As already noted, the shoulder patch is definitely WW II Army Air Corp. I have my father's shoulder patches. He was 9th Army Air Corp, hence his patches had the numeral "9" between the wings.

jmdenver Loc: Colorado

I love all the information. Keep it coming!

robertjerl Loc: Corona, California

And the commander of a large transport ship would be a full commander or captain, but most transports were manned by merchant marine crews with a few military mixed in. If it was an Army transport (yes, the Army had ships) then the crew would be a mix of army and merchant marine.

The ship my unit went to Vietnam on the USNS General W H Gordon started as Navy in WW2 in both the Atlantic and Pacific, went into mothballs, went to the Army to haul troops to and from Germany, then back to the Navy for Korea etc, got modernized etc and hauled troops all over the world (including Indian troops home from Africa for the UN) but mostly to Vietnam after 1965. During all this time most of the crew were merchant marine working for the military transportation people. In fact the Army contracted with the "President Lines" to man and run the ship for them.

When I went to Vietnam on the ship the crew was civilian with about 30 Navy for some jobs and I guess just so they could sort of show the flag for the Navy.