Second-half goals from Josh Magennis and Keane Lewis-Potter moved the Tigers 11 points clear of third-placed Sunderland – who they host in midweek – and 13 ahead of fourth-placed Lincoln – who have two games in hand and welcome Hull next Saturday.
It leaves City needing two wins from their final four games to guarantee promotion back to the Championship at the first attempt.
The hosts looked up against it when Fleetwood took the lead after 22 minutes when Kyle Vassell tapped in following great work on the right from Wes Burns.
But Grant McCann’s side were rejuvenated after the restart and equalised in the 61st minute when Magennis impressively converted Greg Docherty’s defence-splitting pass.
Fleetwood continued to threaten on the counter-attack – Dan Batty earlier had a goal disallowed for offside – but Hull had the momentum and scored the winning goal after 70 minutes.
Dan Crowley’s found a pocket of space on the right and his cross was headed powerfully home by Lewis-Potter.
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