Which of the following is NOT an In-Flight contingency that may be encountered?

Weather changes are typically considered pre-flight considerations rather than in-flight contingencies. In-flight contingencies refer to unexpected situations that can arise once the aircraft is already airborne, directly affecting the safety and operation of the flight.

Aircraft emergencies involve critical situations like engine failure or fire that require immediate pilot attention and action. System malfunctions can relate to failures of various aircraft systems, such as navigation or instrumentation, necessitating specific procedures and responses during the flight. Lost communications may arise from radio failure or other issues, requiring pilots to handle the situation without guidance from air traffic control.

While weather is an important factor in flight operations, changes in weather primarily need to be assessed before flight and included in pre-flight planning to mitigate risks. Once airborne, pilots typically deal with weather through established procedures rather than treating them as contingencies like the others listed.