When is wake turbulence caused by a departing aircraft most severe?

Wake turbulence generated by an aircraft is most severe immediately following takeoff due to the significant amount of lift generated during that phase of flight. When an aircraft becomes airborne, it creates strong vortices from its wingtips as it begins to climb. These vortices, which are a byproduct of the lift, can persist in the air for several minutes and can extend beyond the flight path of the departing aircraft. This means that the turbulence can pose a substantial risk to following aircraft that are taking off or climbing, especially those that are smaller and lighter.

In contrast, during landing, while wake turbulence can also occur, the intensity is generally less severe compared to the moment immediately after takeoff. At cruising altitude, the wake turbulence is not as significant in comparison since the aircraft are more spaced out and usually at higher altitudes where atmospheric conditions can diffuse the effects. Just before touchdown, the aircraft is typically slower and in a different configuration, which can also lead to decreased wake turbulence compared to the initial climb.

Therefore, the correct context for the greatest severity of wake turbulence correlates directly with the phase of flight where lift demands are highest, which is exactly at the moment of takeoff.