First: You MUST clarify if it's at a certain time of day/night. i.e. noon, midnight, etc. Is this at any given point in time?
Top-Down
Population of Delhi/Surrounding areas residents...subset of which would be flying in/out
PLUS population of daily visitors (business / tourist)
% of each group that would need taxis
Multiply out
Divide by time period unit
Bottom-up
When you've been to a large airport, how many landings have you see on the board at one time?
How many per hour?
How many peak hours per day?
How many non-peak hours per day and what % of peak would this be?
# of people in an average plane (i.e. landing)
Multiply out
Divide by time period unit
Is Delhi Airport probably larger or smaller than this sample airport (multiply by that factor)
