1 define the term "visitors", for example, does it only refer to passengers, or airport working staff also need to be considered.

2 segment visitors into three groups (by their objective of visiting): A passengers B friends/ family that come together with passengers C airport working staff;

3 group A guesstimation: from supply side: number of flight that takes on/land in one day * average number of seats per flight * attendance rate (first and third factor could be further segmented according to flight take-off time); or from demand side (harder than supply side): people who leave(tourist leave+citizen leave) + people who arrive(visitor+citizen come home), for citizen part, we could use total number of citizens * percentage, and could further segment with age/ career...

4 group B guesstimation: segment group A's number by age, then for each group, use the "accompany number * passenger number" method

5 group C guesstimation: independant of group A and B; list out departments in airport, and then guesstimate how much staff there will be in each of them

6 add up three numbers: A+B+C; then it will be the result

Hi there,

Providing some market sizing thinking for anyone revisiting this Q&A:

Remember that there's rarely a "best" answer with market sizing. What's important is that you break down the problem the way it makes sense to you. Importantly, break it down so that the assumptions you make are the ones you're most comfortable in.

For example, do you know all the major brands? Great go with that. Do you understand all the segments of that country's population (either age or wealth or job breakdown)? Go with that. Do you know the total market size of the tourism (or hotel) industry? Then break it down that way.

Some tips:

1. Just like in a case, make sure you understand the question - what are you really being asked to calculate
2. Decide whether a top-down or bottom-up approach is best
3. Figure out what you know you know, and what you know you don't know, but could estimate
   1. This helps you determine how to split out buckets
4. Stay flexible - you can start with a "high-level" market sizing, but gauge your interviewers reaction....if it looks like they want you to do more...then go along level deeper in terms of your splits