Which communication system is NOT typically used on Republic Airways flights?

The correct answer is the landline telephones, as they are generally not utilized in the context of in-flight communication systems on Republic Airways flights. In aviation, particularly for commercial airlines, the primary communication methods employed include satellite communications (SATCOM) and VHF radios. These systems allow for real-time communication between the aircraft and air traffic control, as well as facilitating communication between crew members during flights.

Landline telephones, on the other hand, are fixed in location and are not designed for use while airborne. They do not function in the same manner as the other mentioned communication systems that support mobile communication necessary for aircraft operations, especially given the nature of flying. The use of traditional telephones is impractical due to the lack of a physical connection and the operational requirements of modern aircraft.

Therefore, recognizing that landlines do not fit the operational needs and limitations of a flight setting is crucial in understanding why this choice is accurate.