Originally Posted by
f0zzyNUE
No you can't - it seems to be a problem with an AeroMexico flight number that has no seatmap assigned. Have had this happen two times. Only platinum line could solve it by changing the AM flight number in the booking to the KL flight number. It's a general problem with codeshare flight numbers across all airlines.
That's strange. I have an AM booking GRU-MEX-AMS-BCN-CDG-MEX with legs operated by both KL and AF and am able to select seats without issues.