NEW YORK (MainStreet)—Popular belief says that the best days to purchase airline tickets are Tuesdays and Wednesdays, but according to researchers at Texas A&M University, there’s no systematic analys. Another choice is talking to an airline reservationist over the phone or a ticket counter agent at check-in, and as a last resort, a gate agent has the ability to reassign seats right up until boardin. It's easy to change a…