Fleetwood sunk a birdie on the last to join J.B Holmes, who was only through 11 holes, on seven under.
Fleetwood shot four under 67 to take advantage of some favourable conditions on Friday.
He will now await his time slot for Saturday and his playing partners as the second day in Northern Ireland hots up.
Fleetwood dropped a shot on the tough par-three 16th but bounced back to birdie the last and complete a second round of 67.
That set the early clubhouse target on seven under par with Holmes remaining on that score with seven holes to play.
Koepka, who has finished second, first and second in the majors so far in 2019, picked up another shot on the 13th and looked ominously poised to mount another title challenge.
Fleetwood’s own form in the majors this year had been nothing to write home about but a fifth birdie of the day on the 15th took him to seven under and into a share of the lead thanks to Holmes dropping a shot on the ninth.
Woods had picked up another shot on the sixth to reach five over, with the early projected cut at one over.
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