Which of the following is NOT part of the prescribed handoff phrase?

The phrase "Southwest one niner zero" does not conform to the standard format typically used for handoffs in air traffic control communication. Handoffs are designed to provide clear and precise information to ensure that controllers and pilots can easily understand and act upon the information being conveyed.

Key components of a proper handoff phrase often include the distance and direction from a known reference point and specific altitude levels, which facilitate situational awareness. For example, "Five zero miles southwest of OKC" provides distance and direction from a clear point, while "Flight level one niner zero" clearly articulates the altitude. The phrase "Southwest thirty-five" could potentially be interpreted as a navigational heading or instruction, but lacks the meaningful context or specificity of a standard handoff phrase.

In contrast, the option “Southwest one niner zero” is ambiguous, lacking crucial details typically required in a handoff, such as the distance or altitude, thereby rendering it inconsistent with standard handoff protocols.