The Recon Plane supports reconnaissance, with a building effect named All Recon Plane Speed. The first plot requires Base level 7 for construction.
Reconnaissance and normal marches
The game tracks idle reconnaissance squads separately from ordinary squad availability. A lack of idle recon squads is therefore a different message from having no ordinary Squad ready to deploy.
Reconnaissance speed concerns travel for that activity. It is not Hero Squad Size, cargo capacity or an extra combat march slot. The Recon Plane's building power is also separate from the power of a hero formation.
Why the Alert Tower appears in upgrades
Recon Plane upgrades require Alert Tower levels. The plane can therefore depend on tower development even when the resources for its next upgrade are already available.
The target's Alert Tower can disrupt parts of a scout report. That affects the information returned, rather than turning the missing details into zero stats.
Recon Plane buildings have 30 levels and reach 183,900 power at level 30. Additional plots have their own construction requirements.
