I think hot air balloons should enter cantr before helicopter.
I've looked around and did some figuring to raise one cantr person based off some of game concepts and some real world physics. You would need:
about 20kg of silk cloth filled with hot air
and that would cover the weight of the person at full inventory
and 3kg of wood for a carrier of some kind, maybe like a basket.
You would have to build a burner to heat the the air.
I figure 3kg of Aluminum, 40g of rubber and 40g of magnesium.
I also think this would be a good place for a helicopter engine. Better control. Otherwise you would be subject to drift.
Now you would have to add more silk and wood for more people.