Aerial wardriving gives you a 3D signal propagation map that ground surveys can't produce. WiFi signals bleed upward through windows, roof vents, and atriums. Rooftop APs and point-to-point bridges are invisible from the parking lot but wide open from 100 meters up. This is advanced physical-layer recon and it's incredibly effective when authorized. This is a guide on how to aerial warflying / wardriving works.

Comprehensive WiFi security assessment methodology. This is a detailed guide on how to hack WiFi networks.