How Dave's White House plans were changed (as the flight was fully booked...).(News)

Byline: JAMES FORSYTH

There is one aspect of David Cameron's visit to the United States that is puzzling his hosts before he even arrives: why is the schedule being dictated by travel timetables? In a country where the President travels everywhere in a 4,000sqft plane designed to serve as an airborne White House, the idea that everything has to be determined by what flights are available is causing bafflement.

But the Prime Minister is so keen to show that 'we are all in this together' and to prove that austerity begins at home that he is taking commercial flights to America.

The idea will certainly save money, but it is rather restricting his plans. The problem was compounded when Downing Street found out that there weren't enough seats available on the flight that they wanted (maybe Martha Lane Fox, the founder of lastminute.com and now Cameron's internet adviser, can give him some tips on finding tickets online).

The Prime Minister is getting the full treatment in Washington. The new man in No10 will have three hours in the White House and plenty of face-to-face time with the President.

The Obama administration has learned lessons from its disastrous mishandling of Gordon Brown's various visits, which led to snub stories nearly every time.

Cameron and Obama will have a chance to build on the relationship they struck up last month in Canada, when the President gave the Prime Minister a lift in his helicopter from the G8 to the G20 summit.

The British delegation was delighted that the President invited the Prime Minister to fly with him; it was a public display of friendship that showed the Anglo-US relationship is still special (though because there was limited room on Marine One, one poor Cameron staffer was left to find her own way to Toronto).

There had been concern in Government circles that BP and the Gulf oil spill could end up taking over the visit. Cameron has been desperately keen to avoid being dragged into this disaster.

Last month, during his visit to Afghanistan, he was so furious when newspapers called on him to stand up for BP that he refused to talk to journalists accompanying him for the remainder of the trip.

But luckily, BP seem to have had at least some success in capping the well. The spill should not now pollute the visit too much. One Tory Minister joked to me that it was probably Liz Sugg, Cameron's hyper-efficient [pounds sterling]80,000-a-year events organiser, who sorted out the problem as part of her advance work.

The Coalition has also moved to smooth tensions over the release of Lockerbie bomber Abdelbaset Al Megrahi. He was freed last summer on compassionate grounds because he was supposedly dying of cancer. But it soon became embarrassingly clear that Megrahi, who received a hero's welcome on his return to Libya, was nowhere near as close to death's door as had been suggested.

Washington was unhappy at the freeing of a man who had been found guilty of killing 190 American citizens. The issue has been reopened in the United States in the past few days by allegations that BP - yes, that firm again - lobbied the British Government for the agreement under which Megrahi was released to help it get an oil deal in Libya. The US Senate Foreign Relations Committee has announced plans to investigate this charge.

But the British Ambassador has attempted to defuse the situation by saying that the 'new British Government is clear that Megrahi's release was a mistake'. The message is clear: Don't blame us, blame the last lot.

The relationship with America has the potential to divide Cameron from some of his closest colleagues, and from his Coalition partners. Cameron was a reluctant supporter of the Iraq War, unlike his two closest supporters in the Government, George Osborne and Michael Gove, who were both eloquent advocates of it.

The distance between their positions was so considerable that Cameron took to referring to the men in private as 'you neo-cons'.

On the other side of the spectrum is Nick Clegg. During the Election campaign, the Lib Dem leader said it was 'rather embarrassing the way Conservative and Labour politicians talk in this kind of slavish way about the special relationship'.

But these divisions are unlikely to appear as long as Obama remains in the White House. He has chosen to adopt a very different foreign policy from his predecessor; he is not a President who wants to use America's power to reshape the world. With Obama in the White House, Cameron - unlike Blair, Major and Thatcher - is unlikely to have to decide whether or not to support America in a new military action.

In Washington, the consensus is that the administration is unlikely to use force against Iran's nuclear programme.

If the United States did bomb Iran, Cameron would find himself in a near-impossible position. The Liberal Democrats would be urging him to condemn it. But his Defence Secretary, Liam Fox, who has been warning presciently of the Iranian threat for many years, would be unlikely to go along with such gesture politics.

Obama is also keen to end the wars that started on George W. Bush's watch. White House officials have told recent visitors to Washington that the administration remains committed to starting its withdrawal from Afghanistan next year. It is disinclined to listen to the voices of those military commanders - including General David Petraeus, the new commander in Afghanistan, and General Sir David Richards, the new British Chief of the Defence Staff - who suggest this timeframe is too short. This American desire to begin leaving next year fits well with Cameron's aim to have British combat troops out of the country by 2015, as British forces will remain only as long as the Americans do.

When Obama and Cameron first met in July 2008, the Tories were desperate for some of his stardust to rub off on their leader. They were secretly delighted when a microphone captured a relaxed, private chat between the two men. They promoted a video Cameron made about the meeting of the two men, while the Prime Minister's allies called journalists to point out the similarities between the leaders.

But the Obama who Cameron meets this week has lost some of his lustre. More Americans now disapprove of the job he is doing as President than approve of it, and more than 60 per cent believe that the country is on the wrong track.

Oddly, this helps Cameron. Obama now needs events like this visit to go well. Real unhappiness with Obama has also yet to cross the Atlantic. The shots of Cameron and Obama striding across the White House's manicured lawns will still give the PM a boost back home.

Cameron has performed well on the world stage so far. This trip will probably be a successful Washington debut for the Prime Minister. But the country really should give him the prop every world leader needs - a plane.

James Forsyth is Political Editor of The Spectator