The repatriation is set to take place of three British servicemen, one of whom came from Lancashire, who were killed in Afghanistan.
Adjutant General's Corps' Lance Corporal Michael Foley, 25, from Burnley, and Royal Marine Sergeant Luke Taylor, 33, were shot dead by a rogue Afghan soldier at the entrance to the UK headquarters in Helmand Province on Monday.
Captain Rupert Bowers, 24, of 2nd Battalion The Mercian Regiment, was killed just five days before in a roadside bomb blast on March 21.
Their bodies will be flown into RAF Brize Norton in Oxfordshire, where a private ceremony for the men's families will be held before the cortege leaves on its way to the John Radcliffe Hospital in Oxford.
The cortege will be escorted at walking pace past the memorial garden in Carterton where the Union Flag will be hung at half-mast and members of the public are expected to gather.
The shooting at the base in Lashkar Gah was the latest in a string of "green on blue" attacks in which members of the Afghan security forces have opened fire on international allies.
L/Cpl Foley was guarding the front gate of the base when he was killed. Sgt Taylor, from Bournemouth, Dorset, leaves behind his wife Nicola and their son Roan, while L/Cpl Foley, leaves his wife Sophie and their three sons Calum, Warren and Jake.
L/Cpl Foley's family, including his parents Craig and Debbie, sister Lisa and brother Jordan, said in a statement: "Michael passed away while on operational duty in Afghanistan where he was very proud to be serving his country in support of our combined forces in this theatre of operations.
"He will be sorely missed by his family and friends and everyone privileged to serve with him both on his last tour and during his military career."
A total of 407 British troops have died since the start of operations in Afghanistan in 2001