Princes William and Harry cracked jokes with each other as they made multi-billion pound deals for charity on a City trading floor.
A man widowed in the September 11 attacks has returned to the top of the World Trade Center to honour the memory of the wife he lost there.
Actors, sports stars and celebrities have taken to the trading floor during BGC Partners global charity day in London.
The Duke of Cambridge and his younger brother will mark the 12th anniversary of the September 11 attacks on the World Trade Centre and Pentagon by joining traders in London's Docklands to make big deals over the phone.
American global financial services company, BGC Partners, lost 658 employees on 9/11 and has hosted an annual fundraising event in their memory since 2005.
Overall, they have raised £56 million for charity.
Organisers are hoping this year will be no exception - all money generated will be donated to good causes, including SkillForce, of which William is patron, and WellChild, of which Harry is patron.
Financiers BGC Global will be banking on some unlikely new talent to raise funds.
Princes William and Harry are to become stockbrokers for the day at a 9/11 memorial, where they will hit the trading floor to raise money as part of the annual BGC Global Charity Day.
The aircraft part believed to be from one of the hijacked planes that crashed into the World Trade Centre on 9/11 came from a wing, not landing gear.
Police said today that the 5ft part is a trailing edge flap support structure. It is located closer to the body of the plane and helps secure wing flaps that move in and out and aid in regulating plane speed.
Investigators initially thought it was part of the landing gear because both pieces have similar-looking hydraulics.
Workers discovered the part last Wednesday on the ground in a tight space between a luxury loft rental building and a mosque near the World Trade Centre site.
New York police say that part of what appears to be a section of landing gear from one of the jets that were flown into the World Trade Center during the 9/11 terror attacks has been found.
The debris was discovered wedged between two New York City buildings.
An investigation is now under way to see if any human remains can be recovered.
A large piece of airplane debris found close to the World Trade Center site in New York is believed to be landing gear from one of the planes which struck the twin towers in 2001.
The metal part has cables and levers on it and is about 3 feet wide and 1.5 feet deep.
New York Police Department Commissioner Ray Kelly said that it includes a clearly visible Boeing identification number.
Mr Kelly said the medical examiner would check the area around the site to see if it was toxic in any way.
"They will also check to see if there's any human remains at the site and then a determination will be made as to how to move the part from that location".
New York Police Department (NYPD) confirmed that the five-foot-long part was discovered by building surveyors between two buildings on the site where a mosque and community center has been proposed three streets away from Ground Zero.
The part bears a "Boeing" stamp, followed by a series of numbers.
Police spokesman Paul Browne said the NYPD had secured the location and would treat it as a crime scene.
US presidential candidates Barack Obama and Mitt Romney have both tweeted on America's commitment to freedom, 11 years on from the 9/11 terrorist attacks.
As painful as this day is and always will be, it leaves us with the lesson that no act of terrorism can ever change what we stand for. -bo
On this most somber day, America is united under God in its quest for peace and freedom at home and across the world.
US President Barack Obama has told 9/11 victims' families that the whole country shares their loss on the 11th anniversary of the terrorist attacks.
Speaking at the Pentagon, where 184 people were killed, Mr Obama said:
Eleven times we have paused in remembrance and reflection, in unity and in purpose. This is never an easy day, but it is especially difficult for all of you, the families of nearly 3,000 innocents who lost their lives.
But no matter how many years pass, no matter how many times we come together on this hallowed ground, know this: That you will never be alone, your loved ones will never be forgotten.
They will endure in the hearts of our nation because through their sacrifice they helped us make the America we are today, an America that has emerged even stronger.
US President Barack Obama has said the annual act of remembrance for the victims of the 9/11 attacks provides the chance to recommit the nation's values.
In an address at the Pentagon in Washington, Mr Obama said: "No act of terrorism can change what we stand for."