The U.S. Air Force said on Friday that delivery of the first of two new Air Force One jets from Boeing Co has been pushed back another year to mid-2028, the latest in a series of delays.

The Air Force One project involves converting two 747-8 aircraft into a dedicated jet equipped with advanced communications and defense systems. As the next generation of the US presidential plane, the project will be delivered in 2028, four years later than originally planned.

Boeing said the project is making progress. "Our focus is on delivering two exceptional Air Force One aircraft to the nation."

In mid-February, Trump expressed dissatisfaction with Boeing but ruled out European rival Airbus as an alternative. Around the same time, Boeing CEO Kelly Ortberg said Elon Musk, who serves as an adviser to Trump, "helped us a lot" in steering the delivery of the presidential plane.

The U.S. government recently commissioned defense contractor L3Harris Technologies to overhaul a Boeing 747 aircraft previously used by the Qatari government for use as temporary Air Force One.