Freight operator Air Cargo Germany has suspended its operations but has yet to clarify the reason behind the measure.
The carrier, based at Frankfurt Hahn airport, has a fleet of four Boeing 747-400 freighters.
Air Cargo Germany says it has "temporarily interrupted" its flight operations, as of 18 April, but has not indicated whether this is a voluntary decision or a regulatory matter.
"The interruption occurred all [of] a sudden and was not predictable," says the carrier.
"Air Cargo Germany assures a continuous availability for its customers and works on sustainable solutions to recommence the service as soon as possible."
Germany's civil aviation authority, LBA, could not immediately be reached for comment.
Air Cargo Germany linked up with Russian freight specialist Volga-Dnepr last year. It underwent a change of leadership in February with the appointment of Michael Schaecher to replace chief executive Michael Bock.