Thousands of people have gathered at Old Trafford to pay tribute to the 23 victims of the Munich air disaster.
There was a minute’s silence at 1504 GMT, to coincide with the moment of the crash 50 years ago.
Eight United players died – Geoff Bent, Roger Byrne, Eddie Colman, Mark Jones, David Pegg, Tommy Taylor, Liam “Billy” Whelan and, 15 days later, Duncan Edwards – as a result of the injuries they suffered in the crash.
Three members of the club’s staff, eight journalists, two of the flight crew and two other passengers also died.
There was a simultaneous service at the site of the crash and another minute’s silence will be held at Wembley before England’s friendly against Switzerland.
The service in Manchester was led by club chaplain the Reverend John Boyers and the order of service included a message from Prince Charles.
One of those present was former United goalkeeper Alex Stepney, a schoolboy of 15 at the time of the tragedy.
He said: “It’s a sad day, but also a day to remember.
“I am very humble, I was 15 at the time and I remember how shocked everyone was.
“Little did I think or dream then that I would play for the team when they won the European Cup in 1968.”
On a day of commemoration at Old Trafford, the centrepiece will be the unveiling of a permanent exhibition of the Busby Babes in the South Stand tunnel – to be renamed Munich Tunnel.
England and United defender Rio Ferdinand says he hopes supporters at Wembley will observe the minute’s silence before England’s international against Switzerland tonight.
“I’m sure the fans will respect it – it’s a poignant moment and we’ve got fantastic fans in this country,” said Ferdinand.
“It’s not just about Manchester United, it’s about English football too.”
On Sunday, there will be another minute’s silence prior to United’s home Premier League game against Manchester City.