Sadly, the X doesn't mean the seats are "reserved for members of the X-Men," per one Redditor on the r/Delta page. Instead, it's so they can be assigned on the day of the flight, and there are ...

When the Bombardier CRJ-200s are gone, all Delta Connection aircraft will have first-class cabins. Delta will bid farewell to 50-seat Bombardier planes next summer: Travel Weekly Toggle navigation ...