# Estimate the number of airplanes flying currently.

Estimation questions always need some assumptions to proceed and break down the problem. Assumptions are kind of pretty important to make, having a rough idea of Population (Country wise), Internet users, Moneywise segmentation are always good to know. So, continuing with our 12th day of product series with this estimation question.

Just before proceeding, a few clarifying questions, I would like to ask are -

- Do I need to consider planes that are flying in a particular time interval?
**(Interviewer - Your choice)** - Should I consider all kinds of planes like a commercial, cargo, or private?
**(Interviewer - Only commercial)** - Should I go ahead with finding planes that flew from Indian airports only?
**(Interviewer - Go ahead)** - I’m assuming we’re talking about the pre-covid situation only.

Now, I would like to build an equation first, the equation would go like this -

**Number of planes currently in air in India** = No. of airports * No. of runways per airport * No. of planes flying the whole day.

To first calculate the number of airports in India, I would divide all the airports into 3 categories - **Major, Medium & Small.**

Now, need to figure out how many of the planes take off from those runways, to do this we can divide again it into two segments, one could be **peak hours** and the other as **non-peak hours**. Doing the calculation -

Finally, we have to calculate the total number of planes flying in a day from all the airports. To do this we’ll multiply the total no. of planes with the total no. of runways for both peak and non-peak hours.

After doing all the calculations, the number comes out to be **16,065** but this is actually **not the number of planes flying currently**, but this is the total no of planes that fly in a whole day.

Now, this is a little trickier to find planes that are flying currently, so I’ll assume that a flight avg duration is of 3hours, and for the whole day it would be 24/3 = 8 times. Consider it like this, there are a total of** 8 instances** where a plane either land or flies from its runway. So, if we simply divide the total planes flying by 8, it would give us avg no of planes in the air currently at any point of time. *(I’m also not sure about whether this is correct or not, but would love to know the opinion of you all folks there).*

Thus by this way, avg no of planes that are in the air right now is = 16,065/8 ~=**2000 Planes**