Reason being, the pilots are issued official sidearms due to the operational requirement, just like SSG and others using due to the operational requirement for them. Otherwise sidearms have been withdrawn from the conventional forces and MP-5s are to be used in that role. The normal PA/FC officers that you see wearing sidearms are the ones which they have bought for themselves out of their own pockets and the choices ranges from personal choice to the affordability of each officer's pocket. Bought CF98s/Russian Vikings/Makarov/some Turkish ones for some officers myself on their request based on personal choice and in some cases whatever best they could in the given budget.
Nowadays have learnt that units deployed in operational areas have received a few new Turkish origin pistols which are issued selectively on case to case basis, but majority of the officer have now bought one of their own.