How it actually works
You are not flying to Antarctica. You are flying to South America — most commonly Buenos Aires — and then onward to Ushuaia, the port at the bottom of Argentina where the great majority of expedition ships leave from. From India that is two long-haul sectors and an internal one, and it realistically consumes two days each way before the voyage starts.
That matters more than it sounds. The single most common planning mistake is treating the voyage length as the trip length. A ten-day voyage is a sixteen-day trip once you count the flying, the buffer night before embarkation that any sensible planner insists on, and getting home.
The buffer night is not optional. If a flight into Ushuaia is delayed and the ship sails, there is no catching it up.