Extra security was drafted in to ease the concern of fans during the game against Charlton – and another major operation is likely to take place on Saturday when United entertain Liverpool.
It was following a raid on a house in Manchester that police said the Saturday game was a potential terrorist target.
Ten men were arrested and, according to media reports, found to have tickets for seats in different sections of Old Trafford for the game.
United has denied it was specifically targeted by terrorists.
