Why Taranto's aircraft attacked in two waves

Why was the Taranto attack divided into two waves?

Night deck handling and formation were difficult, and too many aircraft over the harbour at once risked interference and a less effective attack.

The split reflected practical limits as well as tactics over Taranto. Illustrious had to range, launch, and organize heavily loaded aircraft on a dark flight deck. Planners also worried that too many slow aircraft over the harbour at once would obstruct one another and reduce attack effectiveness. The two waves balanced the desire for concentration against carrier handling and the need to keep aircraft apart over the target.