This dissertation examined how standard phraseology (SP)—the specialized form of Aviation English used in radio communication—develops during ab initio flight training. The study was three-fold: (1) examining how SP accuracy and fluency developed across three training stages and whether developmental patterns differed between L1 and L2 English-speaking student pilots; (2) investigating how utterance-level performance predicted listener perception of accuracy and fluency; and (3) tracing the cognitive processes underlying SP development within authentic flight tasks. Drawing on Segalowitz's (2010) utterance-perception-cognition framework, extended to incorporate accuracy, the study employed a longitudinal multiple-methods design. The quantitative strand analyzed 5,770 audio samples from 46 student pilots (L1 = 29; L2 = 17) and 18 certified flight instructor-instrument pilots using a purpose-built SP test administered at three training milestones, with certified flight instructor-examiners providing perceptual ratings. Automated acoustic-temporal coding of four accuracy and five fluency measures was examined for alignment with hand coding. Linear mixed-effects models revealed significant improvement across all measures over time, with the steepest gains concentrated in the simulation-only training phase. While L1 participants maintained higher overall performance, L1 and L2 developmental trajectories were broadly parallel, with L2 students showing greater relative growth in reducing omissions. By the final training stage, L1 students were perceptually indistinguishable from experienced instructors on fluency, whereas L2 students remained significantly lower. Omission ratio emerged as the strongest predictor of perceived accuracy, and speed and breakdown features drove perceived fluency ratings. Listener perceptual weighting shifted across training: raters initially penalized discrete errors but increasingly weighted standardization as student performance developed. The qualitative component, a multiple-case study using stimulated recall and reflective journals from three focal participants across five recorded flight activities, examined cognitive mechanisms underlying SP development within authentic flight tasks. Cross-case synthesis revealed three distinct cognitive orientations: action-oriented production under uncertainty, selective comprehension with inference-based learning, and attenuated engagement with instructional dependence. Similar surface-level performance outcomes masked fundamentally different cognitive experiences, with attentional redistribution between language and aircraft operation emerging as a critical factor distinguishing developmental trajectories. These findings advance understanding of SP as a multidimensional construct and offer evidence-based guidance for flight instruction, curriculum design, and aviation language policy.