Interesting... I have a friend trying to join me on an upcoming flight and he's tried to "upfare" two legs where the seat map has 1 available seat but EF has all F/J fare classes zeroed out: (
C0 J0 R0 D0 I0 Y7 B7 H7 K7 M7 L7 G7 V7 S7 N7 Q7 O7 E7)
When he's given a booking that is being sold as F/J, two legs are sold as in economy as a "V" fares.... I find that strange as I was expecting the fare to be "Y" fares.. just in case an F/J fare is pushed out at the last minute."