Fletcher's directing credits include "Eddie the Eagle", distributed by Fox, and "Sunshine on Leith".
Singer, however, accused Fox of not letting him have time off the project to deal with health issues for one of his parents.
A source also tells Variety that Tom Hollander, who was set to play manager Jim Beach, left the film to due Singer's behavior.
Among his acting appearances, Fletcher starred in British children's TV comedy drama Press Gang between 1989 and 1993, later taking roles in gangster movies Lock, Stock and Two Smoking Barrels and Layer Cake, as well as Steven Spielberg's wartime miniseries Band of Brothers.
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"With fewer than three weeks to shoot remaining, I asked Fox for some time off so I could return to the U.S. to deal with pressing health matters concerning one of my parents", he said in a statement. Singer's unexpected absence shut down production, forcing Fox to take immediate action. This was a very taxing experience, which ultimately took a serious toll on my own health.
The film, about British rock band Queen and its frontman, is expected to be released as scheduled on December 25, 2018.
Again, Fletcher is a more than capable replacement for Singer, as Eddie the Eagle is better than anything Singer has directed in years.