The US has formally sent to trial five suspected al-Qaeda militants believed to have planned the 9/11 terror attacks.The five Guantanamo Bay inmates, including alleged mastermind Khalid Sheikh Mohammed, will be tried by a military commission.They will face charges including terrorism, hijacking, conspiracy, murder and destruction of property.They could face the death penalty if found guilty, the Pentagon confirmed.Khalid Sheikh Mohammed and the four others - Waleed bin Attash, Ramzi Binalshibh, Ali Abd al-Aziz Ali and Mustafa Ahmad al-Hawsawi - are expected to be tried together, the Pentagon added.They are accused of planning and executing the terror attacks of 11 September 2001, which saw hijacked planes strike New York, Washington and Shanksville, Pennsylvania.A total of 2,976 people died in the attacks.The decision to refer the charges to a military commission comes after a legal wrangle over where the five men would face justice.The Obama administration initially tried to move their trial into US civilian courts, but reversed its decision in April 2011 after widespread opposition.The five were eventually charged in June 2011 with offences similar to those they were accused of by the Bush administration.US President Barack Obama came into office in 2009 pledging to close Guantanamo Bay and try high-value terror suspects in US civilian courts.But he was forced to abandon the closure plans as it became apparent that the issue of where to imprison and try al-Qaeda suspects had no easy resolution.