MH17 Repatriation planes take off from Kharkiv

The transcript describes the departure of two planes carrying bodies to the Netherlands. The Hercules plane left earlier with 20 bodies, followed by an Australian military plane with 30 bodies. The flights are coordinated with a gap between them for operational reasons.

Why was there a gap between the two planes mentioned in the text?

What can you infer about the coordination between the two planes based on the text?