On Functioning Form, I discuss smart defaults (selections put in place that provide answers to questions for you) in registration & travel booking forms. Check out the full articles:

Smart Defaults in Registration Forms
When electing to join the Naymz site from an email invitation, you only need to select a password. Your name and email address have been filled in for you...

Smart Defaults in Travel Booking Forms
Now last I checked, the majority of people booking flights online are adults and they generally intend to travel on the flight they book...