I'm booking a flight MAN>IBZ and when it came to select my seat, which is usually 1A if I'm quick enough, I noticed it wasn't shown on the seating plan. 1B and C were, so I took 1B. Also 2 DEF were missing. There wasn't an "X" showing that it had already been booked, the seats were simply absent. Is there a reason for this, and will they possibly be available later to book? Thanks!