A carrier with Force Z would have controlled its fighters by radio during the Japanese attack. Fighters listening near Singapore could hear that activity and recognize that a battle was underway. Their Buffaloes could then join the carrier's Sea Hurricanes or Wildcats. In this counterfactual, the carrier improves coordination with land-based aviation as well as supplying its own fighters.
Notable Point · 2:41:21-2:42:03
How carrier fighter direction could bring Buffaloes to Force Z
Carrier radio traffic could alert Singapore's Buffalo fighters and bring land-based reinforcements into the battle.