Atlas Air Worldwide Holdings has grounded four converted B747-400(F)s since the beginning of the year and will shortly return one more to its lessor as the US-based holding adapts to a slower global freight market, Chief Executive John Dietrich said during a quarterly earnings call.

"As we talked about throughout the latter part of last year, demand has been softer. And when in that environment, it's usually the least efficient aircraft logically that get parked first. And frankly, the demand has not been there for those aircraft, so we elected for the B747 converted freighters to be temporarily parked as we manage through the current period," he said.

The CEO explained that the converted freighters were heavier and less efficient than the purpose-built B747-400(F)s. Also, the converted aircraft lack a nose cargo door. However, the aircraft will be available to return to service with "appropriate lead times".

"We [also] have sold or expect to sell three non-essential aircraft in our dry lease portfolio," Dietrich added.

Specifically, the airline has already sold a B757-200(F) and plans to sell one B737 passenger aircraft and one B777-F.

Atlas Air Worldwide Holdings owns three airlines: Atlas Air (5Y, New York JFK), Polar Air Cargo (PO, New York JFK), and Southern Air (9S, Cincinnati Int'l). Of these, Atlas Air operates both cargo and passenger aircraft, while the other two carriers cater exclusively to the freight market. The group also owns Titan Aviation Holdings, a lessor which owns aircraft operated both by Atlas Air Holdings members and third-party carriers.