The Phase-III version of the constitution class using the LN-72 warp engines, and a "stealth" color scheme for space combat.
The MacArthur class was built after the Excalibur class USS MacArthur engaged what her captain thought was a trio of D-7 battlecruisers in 2073. Unfortunately for the USS MacArthur the ships were K'Tinga class and were thus superior to the Excalibur class (Phase-I) Constitution type of advanced cruisers. The out classed USS MacArthur was badly damaged during the fray and was forced to retreat from the system along the Neutral Zone that she engaged the three K'Tinga class warships. After the encounter, Starfleet chose to upgrade the USS MacArthur to the Phase-II (Enterprise type from the Motion Picture), however, the V'Ger incident exposed some of the shortcomings of the Phase-II refit and thus a Phase-III plan was put into action. The result was the MacArthur class of 2076.