This study investigated the impact of two instructional techniques (synonym/antonym vs. input enhancement) on ESP students’ aviation vocabulary learning. Furthermore, it meant to specify the Vocabulary Learning Strategies (VLS) most frequently utilized by the participants. The study included sixty male aviation ESP Learners, who were randomly put into three groups (one control and two experimental ones). Sixty new aviation lexical items were administered to the learners in the form of a Vocabulary Knowledge Scale (VKS). Forty aviation vocabulary items were chosen to construct a multiple-choice test to be applied as pre- and post-tests. To examine the frequency of VLS, the researchers made use of a VLS questionnaire. The results indicated a substantial enhancement in the performance of the experimental groups versus that of the control group, which reveals the noticeable role of contextual and textual clues in ESP vocabulary learning. Moreover, the findings pointed out that the input enhancement technique was superior to the synonym/antonym technique. Finally, similarities and differences were detected between the experimental groups regarding frequently-used VLS. The findings of the study has implications for ESP teachers, students, and syllabus designers.