Add Yahoo as a preferred source to see more of our stories on Google. Passengers check in at O'Hare International Airport in Chicago. (Scott Olson/Getty Images) (Scott Olson via Getty Images) There ...

HOUSTON — If you're taking a flight on United Airlines soon, you'll want to get to the airport a little earlier than usual after the airline's new check-in policy went into effect on Tuesday.

"Check-in chicken" is a strategy where travelers wait until the last minute to check in, hoping for a better seat assignment. The only guaranteed way to get a preferred seat is to pay for a seat ...