score:6
It isn't first class, it is a mistake made by ITA Software (unusually) in mapping the booking class (F
) back to the cabin class (for JQ, booking class F
is economy). A similar mistake is made by a few online travel agents for Aer Lingus which also uses F
for economy.
Looking at ExpertFlyer it seems that JQ uses J
and D
for business; Y
, B
, V
, T
, S
, R
, Q
, P
, O
, N
, M
, E
, F
, L
, A
, Z
, I
, K
and H
for economy, in order from most to least available.
The GDS guide you've linked is from 2014, they may have amended their codes since then; or it may be that the F class is not used for publicly sold fares.
You may want to report it to ITA as a bug.