Louis van Gaal reportedly ordered his players to attend a training session as soon as they touched down from an eight-hour flight back to England.
Manchester United's squad have spent the last couple of weeks in America for the International Champions Cup, but returned to the UK following their defeat to Paris Saint-Germain.
The Manchester Evening News reports that Van Gaal told his squad once they were on the plane that they would be heading straight to the club's Carrington training ground as soon as they arrived, which was not well-received by some of his players.
United host Tottenham Hotspur in the opening match of the new Premier League season on Saturday.
