FLETC (pronounced FLET-see) stands for Federal Law Enforcement Training Center.
The bartender refers to the patrons in the bar as the "pau hana crowd". Pau hana translates as "being finished with work", it is essentially the Hawaiian way of saying the bar was having happy hour.
The F-35c is a new variant of the Lockheed Martin F-35 Lightning, the F-35c's modifications were made specifically for the US Navy. The Lightning is a single-seat, single-engine stealth multirole combat plane, it can act as both a fighter, bomber and interceptor. The F-35c is designed specifically for launching from and landing on an aircraft carrier, which the previous versions are not capable of. The main difference is the F-35c has a larger wingspan, previous F-35's have a 35 foot wingspan, the 35c has a 43 foot wingspan; the wings on the F-35c can also fold up partially to make them better fit in the limited storage space on a carrier.
Before joining NCIS Agent Holman was in the Marine Corps, after serving two standard duty tours he said he joined Marine CID. He is referring to the United States Marine Corps Criminal Investigation Division, a federal law enforcement agency that conducts crimes committed by or against members of the US Marine Corps or Marine Corps property. Being a part of the Department of the Navy, Marine CID is a secondary agency to NCIS, they conduct investigations into misdemeanor and felony crimes that NCIS has not assumed jurisdiction of; typically NCIS only takes jurisdiction over serious felonies related to the Marine Corps such as rape and murder. The Marine Corps CID's mission statement is: "conducting criminal investigations related to violations of the Uniform Code of Military Justice by United States military personnel on Marine Corps installations; violations of US Code by civilians aboard Marine Corps installations; force protection efforts by the collection of criminal intelligence; investigative lead tasking; and activities in coordination with other local, state, federal, and host nation law enforcement agencies."