Flying lad: A-340´s CFM 56-5-C4 are flat rated at ISA+15.
Zeke: I think that those numbers,A-320 ISA+45 and A-330 ISA+43, are T MAX and not T REF.
¨[For non Airbus Pilots,
T MAX:Maximum assumed (flex) Temperature.(ISA+40 in the 340.)
T REF:Flat Rating.]