With all of her more senior colleagues out of the country, Bennett is in charge of the country for 24 hours.
She is the fifth-ranked MP in Cabinet.
Prime Minister John Key is in India with a business delegation, Deputy Prime Minister Bill English and Steven Joyce are in Australia for a leadership forum, and Gerry Brownlee is returning from a counter-ISIS conference in France.
Brownlee will return tomorrow morning to take over the reins.
The last time a fifth-ranked MP was made Acting Prime Minister was when Tony Ryall was in charge for three days in 2009 while the top four ministers were in Australia.