A fifth G600 flight test aircraft and the first to be equipped with a full interior has joined Gulfstream’s campaign to certificate and begin delivering the ultra-long-range business jet next year, the Savannah-based manufacturer announces.

The flight of a test aircraft bearing a full interior is usually a sign that a manufacturer is well along with a certification campaign, as the interior is one of the last systems on a modern aircraft to enter airworthiness trials.

So far, Gulfstream’s first four G600 test aircraft have accumulated 790 flight hours on 180 test flights, Gulfstream says.

“Our extensive testing will validate design and performance, so we can provide a cabin that exceeds expectations,” Gulfstream president Mark Burns says in a released statement.

The test flight comes nearly three years after Gulfstream announced the existence of the G600 and its smaller sister aircraft – the G500 – in a factory ceremony in October 2014. Both aircraft feature new technologies, such as a wider fuselage cross section, active control sidesticks and advanced information management systems embedded within the flight controls.

The G500 is on track to receive certification and begin deliveries by the end of the year, followed by the G600 a year later.