The Prince of Wales is to try to cut travel costs by using a personal friend's private plane for an official visit to the US, his spokesman says.
Texan financier Joe Allbritton offered the heir to the throne his seven-seater jet for the trip to Washington in May.
It is thought to be the first time a member of the royal family has used an aircraft provided by a private individual for an official visit.
The prince will meet the US president and address an agriculture conference.
Clarence House confirmed Prince Charles will pay nothing towards the cost of the flight.
His speech at Washington's Georgetown University is expected to encompass international sustainability, links between the British and US armed forces, the welfare of injured servicemen, and education.
The Green Party has criticised the prince's choice of travel, which it says would create a greater carbon footprint per passenger than taking a larger commercial plane.
A spokeswoman said: "It's very commendable of Prince Charles to think about the costs of flights to the taxpayer, but being an environmentalist, I would have thought he would have looked very carefully at the carbon costs of taking a small private jet to the US.
"And frankly, if he really wanted to save the taxpayer money, he could pay for the costs himself."
The prince's communications secretary Paddy Harverson said: "In the current economic climate it was felt it was right to accept the offer [of the plane].
"Needless to say, our friendship with the United States is one of the most important of Great Britain's international relationships."
And he added: "We always do consider the carbon impact of our travel plans, but we have to take into account a number of important factors when deciding how to travel, such as security, and the guarantee of prompt departure and arrival times.
"When these and other factors are taken into account, we decided that the use of the private charter was the best practical option to ensure the trip could go ahead smoothly."
The trip, from 3-5 May, comes just days after his son Prince William's wedding and will also involve attending an event to support British and American armed forces deployed overseas.
In 2007, the prince took a three-day trip to the US, delivering a speech at the National Constitution Centre in Philadelphia and accepting an environmental award from Harvard Medical School's Center for Health and the Global Environment.
On that occasion, the prince travelled to the US on a scheduled British Airways flight from Heathrow, although its departure was delayed by nearly an hour.
He was accompanied by his wife, the Duchess of Cornwall, on the previous trip, but she will not be joining him on this visit.
President Barack Obama is due to make an official state visit to the UK at the end of May.