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How many people are flying in the air right now?

How many people are flying in the air right now?
Can someone please help me in solving this estimation question?

My approach was the following

Total number of airports in the world x the number of planes flying in air / airport x the number of people / plane. 

I am struggling to get the number of planes flying in air. Would love to hear your approach in getting this number or in suggesting another approach to solve this case.

All the best.

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Top answer
John
Coach
edited on Aug 27, 2019
Ex Bain Case Team Leader I Focus on Private Equity I +80 interviews conducted at Bain I All cases based on real life cases

Hi,

I would go with 

1) Number of people in the world 7.5B

2) Segment them into (non flyers ~85%, occasional flyers 14%, frequent flyers 1%)

3) Multiply with number of flights (no flyers, occasional flyers 4, freqeunt flyers 10)

4) Multiply with hours per flight (5 hours)

5) Divide by hours per year (365 *24= 8760)

6) Multiply with share of flight time that you are actually not in the air (i.e. on the runway) - let's say half an hour out of 5  - so multiply with (4.5/5)

So the the whole equation looks like:

7,5 * (0,14*4*4/8760+0,01*10*4/8760) * (4.5/5) = 2,542,808-> ~2.5 Million people in the air right now.

You will note that it is quite hard to come up with very accurate estimates in 2) 3) and 4) but probably easier than trying to estimate number of airports and number of flights per airport.

Hope this helps.

John

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