While at the airfield, Milley met with troops and personnel and examined the shipment activity, the official said Friday.
The site has become a beehive of activity in recent days, going from a handful of flights each day to as many as 17, the field's maximum capacity.
The airport's location remains a secret to protect the shipments of weapons, including anti-armor missiles, into Ukraine.
The Russian military has not targeted these shipments once they enter Ukraine, the official said, but there is some concern Russia could begin targeting the deliveries as its assault advances.
The flights have been repositioning troops along NATO's eastern flank, but also moving weapons to the transfer points where they can be delivered to Ukraine.
The pace of the flights has only increased.
US European Command (EUCOM) is at the heart of the massive shipment operation, using its liaison network with allies and partners to coordinate "in real time" to send materials into Ukraine, a second Defense official said. »