India, Oct. 22 -- Airlines charging hidden fees is a common practice now, with a staggering 89% of airlines worldwide charging for one or more add-ons, according to Euronews. From choosing your seat to checking in a bag or booking for a child, these charges are not exactly hidden, but they're rarely shown in the headline fare. Here's a breakdown of the most common airline extras; and what you should watch out for before you hit "pay":...