In which case might an engine be considered critical in jet engines?

An engine can be considered critical in jet engines primarily during takeoff. This phase of flight is crucial due to the significant thrust required to lift the aircraft off the ground and the proximity to the ground, where any thrust imbalance or engine failure can lead to a loss of control.

In the event of an engine failure during takeoff, pilots may need to maintain directional control, and the performance of the remaining engine(s) becomes vital for a successful takeoff and a safe climb-out. Therefore, it's essential to understand that the most critical time for an engine's functionality is when the aircraft is in this high-stress situation of takeoff.

While strong crosswinds and severe storms present challenges that require the pilot's attention and skill, the fundamental aspect of engine criticality revolves around the takeoff phase, where any failure can lead to catastrophic consequences.