The first Boeing KC-46A Pegasus test tanker has returned to the skies over the US state of Washington with a four-and-a-half-hour airworthiness flight on Thursday and another flight late on Friday, the company says.

The Boeing 767-2C, known as EMD-1, first flew in late December with a flight from Paine Field in Everett to Boeing Field in Seattle. Company spokesman Chick Ramey told Flightglobal today that the aircraft resumed airworthiness flight testing this week to assess the aircraft’s handling qualities and functionality.

“Next up for EMD-1 is a flight with the aerial refueling boom and wing pods installed,” says Ramey. “That flight is part of the planned process to certify the 767-2C’s airworthiness.” The Thursday flight left from Boeing Field and landed in Everett.

The first flight with the aerial refueling boom and wing aerial refuelling pods (WARPs) is due to occur in the coming weeks.

KC-46 F-35s - Boeing

Ramey says this week’s flight could be confused with the first KC-46 tanker flight with the EMD-2 test aircraft scheduled to occur later this summer, several months behind schedule.

Boeing is to deliver four test aircraft as part of the engineering and manufacturing development (EMD) phase for the next-generation tanker, which is designed to replace the KC-135 tanker that has been in service since the early days of the Cold War.

Ramey says the company expects all four EMD aircraft to fly this year, two as 767-2Cs and two in the full KC-46A configuration. Boeing is on contract to deliver 18 combat-ready tankers to the air force by 2017 and the total requirement of 179 KC-46s by 2027.