How can you know if an aircraft is half full or not, months before flying? You cannot tell just by looking at the 'choose your seat' section'. The only way you could find out this information out is by asking an airline booking representative, and it's not certain that they would divulge this information in the first place. Many customers don't choose their seats until the 48 hour check in before the flight. A high proportion of customers don't use 48 hour check-in and are allocated their seats when checking in at the airport.