Volga-Dnepr upgraded the capacity of a second An-124 aircraft by 20 tonnes.
The upgrade means the aircraft will now be able to carry a maximum total cargo payload of 150 tonnes.
Work carried out on the aircraft includes a new re-enforced floor and tyres.
The carrier said that it planned to upgrade another of its 12 An-124s this year while past reports suggest that work will also be carried out on a fourth aircraft.
When announcing the upgrade of it its first An-124 in June last year, the carrier said that the flight range has also been increased, while a single piece of cargo weighing up to 120 tonnes can be transported.
The dimensions of the cargo cabin are: 36.5m x 6.4m x 4.4m, while its crane capacity is 20 tonnes.