According to publically available data ZZ336 not flown since 6th Sept when it did 4hrs BZN-BZN and a return trip to Han(n)over. May have been reasons why an ostensibly civilian aircraft was preferable. May have been the number of PAX travelling it has 50 v Vepina's 58 business seats for the official party. A stopping flight with partial fuel load is sometimes better in fuel burn terms than a fully loaded direct one. It was only on the ground for a short time but there may have been an off the record meeting. Too short a stop for a shopping trip
.