I had a similar case with McKinsey 5 years ago, so I think I can share some details given how long ago it was (2nd round, partner interview).

A lot depends on where the partner leads you. There are many ways to do the estimation, but if the partner leads you in a certain direction, you need to follow it. In my case, the partner ignored my attempts to do the estimation from the demand side and asked to identify and estimate from the bottleneck perspective. The bottleneck for airport is, as was correctly mentioned above, runways - you probably experienced many times the need to sit in the airplane and wait when a runway becomes available.

So, the rough equation would be: # hours an airport operates * # runways * (# minutes in an hour / # minutes it takes a plane to take off/on) * # passengers per plane * load factor. That's the generic approach, now you can adjust it to account for non-passengers, support staff, by, for example, finding out a number of passengers and then assuming a ratio of passengers to non-passengers.

[hours open] * [#runways] * [60m/T or L time] * [#people per plane] * [uti % plane and runway]
20 * 8 * (60/10) * 250 * 90%
~ 215K per day.

I just double checked on Google AFTER this, and it's 213K/day. So pretty close.

Hi Anonymous,

I agree with the points mentioned by Sidi; as for how to calculate peak times vs non peak times, domestic vs international, high capacity vs low capacity, etc I would recommend the following:

• Identify the different segments – eg high vs medium vs low capacity
• Define a value for each of them – eg high: 400; medium: 300; low 150
• Provide a percentage for the frequency for each. Most of the time a normal distribution will work fine. High: 20%; medium: 60%; low: 20%

Performing the math: 80+180+30 =290. You could then ask if you can round it to 300.

I would recommend doing this before saying what is your expected number, and not after, otherwise you may find a final number different from the first you mentioned.

Best,

Francesco

Hey,

I fully endorse Sidi’s point... just let me add you that if I was the interviewer you would get extra points if you are able to identify that crew members can repeatedly be the same in several flights - thus to illustrate what can be considered extra valued on such estimation question (ie, to differentiate a good from an outstanding candidate)

Best

Bruno

I think general approaches here are fine. The key is to understand whether this is a 2-5 mins question or a 20-30 minute case. If latter then go down the whole route of segmentation of plane size, busyness of week days/period of year, otherwise just mention those a potential interesting points and go with big averages.

hope it helps,

andrea