According to the Assyrian King List [http://oracc.museum.upenn.edu/riao/kinglists/assyriankinglist/assyriankinglist/index.html#Ashurdan] (AKL), Ninurta-tukultī-Aššur, son of Aššur-dān I [http://oracc.museum.upenn.edu/riao/thekingdomofassyria13631115bc/ashurdani/index.html], was the eighty-fourth ruler of Ashur. For information about the length of his reign, see introduction [http://oracc.museum.upenn.edu/riao/thekingdomofassyria13631115bc/mutakkilnusku/index.html] to his brother Mutakkil-Nusku.
The AKL records the that Ninurta-tukultī-Aššur was driven into exile in Babylonia by his brother Mutakkil-Nusku [http://oracc.museum.upenn.edu/riao/thekingdomofassyria13631115bc/mutakkilnusku/index.html]. Before that, while Ninurta-tukultī-Aššur held authority over Assyria (possibly as regent), the statue of Marduk that Tukultī-Ninurta I [http://oracc.museum.upenn.edu/riao/thekingdomofassyria13631115bc/tukultininurtai/index.html] had taken to Ashur was returned to Babylonia (Grayson 1975, 176: 12-13). That act presumably garnered him favor with the king of Babylon since that ruler wrote a few letters to the Assyrian king, possibly Mutakkil-Nusku, on his behalf while he was exile. The vindictive tone of these badly damaged pieces of royal correspondence suggests that the Babylonian king intended to install Ninurta-tukultī-Aššur as the king of Assyria (Grayson 1998-2001, 527). Those plans were never realised and Aššur-rēša-iši I [http://oracc.museum.upenn.edu/riao/thekingdomofassyria13631115bc/ashurreshaishii/index.html] became king when his father Mutakkil-Nusku died.
Poppy Tushingham & Jamie Novotny
Poppy Tushingham & Jamie Novotny, 'Ninurta-tukultī-Aššur', The Royal Inscriptions of Assyria online (RIAo) Project, The RIAo Project, a sub-project of MOCCI, 2017 [http://oracc.museum.upenn.edu/riao/thekingdomofassyria13631115bc/ninurtatukultiashur/]