McDowall's previous roles at Air New Zealand include group general manager corporate finance and group general manager commercial.
Prior to Air New Zealand he worked across a variety of industries in Asia, the United States and the United Kingdom.
General manager corporate finance, Stephan Deschamps will take over as acting chief financial officer on the executive on September 26.
Air New Zealand reports its full annual result tomorrow morning.
Luxon, who announced his resignation in June, took over as Air New Zealand's chief executive in 2013 after two years working as its international head.
It has targeted pre-tax earnings to exceed $340 million after downgrading guidance due to rising fuel prices, disruptions to airline schedules over global engine issues, and slowing domestic travel.