Producing adenovirus gene therapy vector in producer cells that express or over-express adenoviral polypeptide IX enables one to produce pIX-deleted adenovirus in suspension cell culture. Using producer cells that express or over-express adenoviral polypeptide IX also increases the yield of adenovirus vector, regardless of whether that adenovirus is pIX-deleted. Using producer cells that express or over-express adenoviral polypeptide IX also improves the resulting vector's transduction kinetics, reducing the number of pfu/target cell required to achieve a given level of transduction/infection, shortening the time the vector requires to transduce or infect a target cell, and shortening the time an infected target cell produces progeny virus.