Modi has had a full dance card recently.
Fresh from hosting the BRICS summit in Goa, including China's Xi Jinping, Russia's Vladimir Putin, Brazilian President Michel Temer and South Africa's Jacob Zuma, next up after Key will be Theresa May, leading a delegation keen to signal the UK's post-Brexit intentions.
It's easy to see why a queue is forming. India is the world's third-largest economy and by 2022 is forecast to have the world's largest population, with the average Indian's spending power growing by 42 per cent since 2011.
However, despite being business focussed, the Modi Government has not sped ahead with free trade negotiations with a range of countries.
It has a "Make in India" doctrine focussed on direct investment rather than trade.
Before his meeting with Modi, Key will be given a ceremonial state welcome, and lay a wreath at Gandhi Memorial.
Later, he will speak at an NZ-India business leaders summit.
The surprise visit of a world leader made waves in North Queensland.
The Townsville Bulletin today published a front page picture of Key headlined "India's loss is our gain as NZ PM backs direct flights", after a journalist tracked him down to a local bar last night.
Key told the paper he would like to see direct flights between Townsville and New Zealand.
The 35-strong business delegation includes former Black Cap captain Brendon McCullum.The New Zealand Air Force has two Boeing 757s in service which, together with a modification project, cost $221 million.
Delegates arriving at Townsville for today's flight took the chance to take a rare photograph of both planes next to each other on the tarmac.
Key and the group left New Zealand on Monday, and will arrive home on Friday night NZ time. The delays mean less than two days will be spent on the ground in India.