Tobzalp. I have never seen a TAS anywhere near that low (380 knots), either on a flight plan or in the FMC with a very low cost index. Perhaps with a u/s pack and we are flying at or below FL 250, but certainly not at normal cruise levels.
Typically with a strong head wind, cruise TAS would be around 450-460 and with a strong tail wind around 430 - 440 (depending on weight , level and type etc).
Not trying to be smart, just letting you know what we see.