 On 28 April 2019, Fleck saw his second promotion in three seasons with United, this time to the Premier League, the club returning after a 12-year absence.On 22 February 2020, Fleck signed a new three year deal 

After playing for Scotland at under-21 level, Fleck was called up to the Scottish senior team for the first time in November 2018.He did not play in that match, and had to decline an invitation to join the squad in May 2019 as it clashed with his wedding in Ayrshire, arranged two years earlier when he seemed far less likely to be involved with the national team.