X and I are both Award tickets, X economy, I business class. Not sure about P, I guess award tickets in Plus?

Current SAS booking classes are:

Short haul
SAS Plus: C, J, Y, S, B, P, A

SAS Go: E, M, H, Q, V, W, U, K, L, T, O, G - group, X

Long haul

SAS Business C, D, Z, I

SAS Plus: Y, S, B, P

SAS Go: E, M, H, Q, V, W, U, K, L, T, O, G - group, X

I also did not find N or R.