Smart Defaults for Flight Passengers

When you start booking a flight ticket, it is obvious that at least 1 person is about to travel. Why ask the user to mention how many adults to start with?

Wego app defaults the passengers field to 1 Adult. Based on analytics data, apps can also change this number to 2 Adults or more. For e.g. if Ryan Air app knows, based on historical data that repeat users usually book as two adult passengers, they could default this value to 2. 

In few scenarios, the user might need to change the values, but that is okay as long as that percentage of users is too few.

What kind of smart defaults do you support?