Sir Bobby Charlton has written an emotional letter to Manchester United's players and staff to remind them of the "devastating effect" the Munich Air Disaster had on the club ahead of the 60th anniversary of the tragedy.
United will mark the date on Tuesday with a service at Old Trafford attended by fans and players as well as Jose Mourinho and his staff.
Mourinho and club captain Michael Carrick will lay wreaths and there will be readings from former manager Sir Alex Ferguson and executive vice-chairman Ed Woodward.
Charlton survived the crash on Feb. 6, 1958 that killed 23 people, including first-team players Geoff Bent, Roger Byrne, Eddie Colman, Duncan Edwards, Mark Jones, David Pegg, Tommy Taylor and Billy Whelan.
"I wanted to take the time to write to you as we approach the significant date of February 6, in which Manchester United and the footballing world remembers and respects the Munich Air Disaster, which tragically affected this great club 60 years ago," Charlton wrote.
"Whilst I'm sure you have read and watched documentaries on this truly awful disaster, words cannot describe the devastating effect that this had on the football club and the lives of those affected.
"Whether on board the plane that evening, or in the aftermath for those and their families and friends, this disaster was life-changing for so many of my good friends and colleagues.
"The devastating effect still lives on and this great football club, which you are part of, has risen from its darkest hour in a way like no other.
"Now, as the time comes to once again remember and pay respects to those victims and survivors of this disaster, I wanted to thank you in advance for the role which you and your teammates will play in the upcoming tributes."
As well as the memorial service on Tuesday, United's under-19 team will visit Belgrade -- where the "Busby Babes" played their last game before the crash.
There will be a reception at the same hotel where Sir Matt Busby and the team stayed in February 1958 before coach Nicky Butt and the players visit the Partizan Stadium to observe a minute's silence and lay a wreath.
The stadium was the venue for the European Cup quarterfinal against Red Star Belgrade in 1958.
Marcus Rashford will be part of the squad at Old Trafford on Tuesday.
The 20-year-old has grown up at United after coming through the academy and says the players are always aware of the impact the disaster had on the club.
"There were already little things about it around the club but then you start to learn about it," he said. "When you got to 15 or 16, that was when [former academy coach] Paul McGuinness really started to bring it to our attention.
"We used to watch a lot of videos of their games, especially from their FA Youth Cup runs, so we could see footage of what these players were like when they were young.
"It touches your heart and helps you understand it, even though you weren't there."