LDOs perform tasks similar to those of warrant officers (WO), but the formal definition differences are subtle and focus on the degree of authority and level of responsibility, as well as the breadth of required expertise.
Prior to World War II, a LDO could only advance as far as lieutenant (O-3E) in the Navy and captain (O-3E) in the Marine Corps.
The Navy Mustang motto is "sursum ab ordine" which means "up from the ranks" to underline a distinction between Navy Mustangs and those Naval and Marine Corps officers commissioned directly from collegiate programs such as the United States Naval Academy, United States Merchant Marine Academy, Naval ROTC and Marine Corps Platoon Leaders Class, and similar post-collegiate pre-commissioning officer candidate programs of the Navy and Marine Corps such as Officer Candidate School and the former Aviation Officer Candidate School.
[2] In general, they may succeed to command activities which have a primary function corresponding to their Navy officer designator or Marine Corps MOS.
In the U.S. Marine Corps, CWOs must serve a minimum of 8 years from the day they were initially promoted to WO in order to be eligible for the LDO program.