An RAF Voyager aircraft that has been refitted for the PM, senior ministers and members of the Royal Family to use is making its maiden flight this week.
The militarised Airbus A330 jet was revamped at a cost of about £10m.
The government has said the move will save about £775,000 a year as it is cheaper than chartering flights.
David Cameron, Foreign Secretary Philip Hammond and Defence Secretary Michael Fallon will fly in the Airbus to the Nato summit in Warsaw on Friday.
The conversion was announced at the end of 2015 as part of the strategic defence and security review.
It has involved 58 business seats being fitted, with the Ministry of Defence saying this will "allow it to transport sizeable business delegations".
It will also be available for official overseas visits for members of the Royal Family.
The PM's flights, using either Royal Squadron planes or long-haul charter, cost on average £6,700 per flying hour, a source said, and the RAF aircraft will cost £2,000.
'Representing the UK'
The Voyager, which will be based at RAF Brize Norton in Oxfordshire, will be available for what the MoD said was its "primary operational role" of air-to-air refuelling when not in use by ministers or royals.
Air Marshal Sean Reynolds, deputy commander capability, said: "The reconfigured Voyager flying on its maiden VIP flight on Friday will proudly represent the UK and the RAF across the globe for many years to come."
The Voyager, a converted Airbus A330-200 airliner, is almost 60m (197ft) long and has a 60m wingspan.
When he was prime minister, Gordon Brown cancelled plans drawn up by his predecessor Tony Blair to buy two private jets, which had been nicknamed "Blair Force One" in reference to the aircraft used to fly the US president, Air Force One.