The International Civil Aviation Organization (ICAO) has established English Language Proficiency Requirements (LPRs) for all flight crews operating on international routes, all air traffic controllers who communicate with foreign pilots, and air professionals. The ICAO requires those who operate on international routes to be qualified at least in Operational Level 4 in the Requirements. However, in Thailand, the only English test that all flight attendants are necessitated to take is the Test of English for International Communication (TOEIC). Apparently, there is a mismatch between the TOEIC test scores and the ICAO Language Proficiency Requirements (LPRs) as the foci of these two differ. The current study thus explored the relationship between the ICAO Language Proficiency Requirements (LPRs) and TOEIC scores of flight attendants in Thailand and their attitudes in order to better determine if the TOEIC is the most effective means to recruit flight attendants in Thailand. The data were collected from 100 Thai Airways International flight attendants using a four-point Likert scale self-assessment survey to measure the participants' self-assessed abilities on all the ICAO rating scale descriptors focusing on Operational Level 4. The data were quantitatively analyzed with inferential statistics of Pearson's product moment correlation coefficient. Moreover, to elicit in-depth information regarding the attitudes of Thai airways flight attendants, the semi-structured interview protocols were also used and subsequently analyzed by means of content analysis. The findings of the current study revealed that there is a positive correlation between the ICAO Language Proficiency Requirements (LPRs) and the TOEIC scores of Thai Airways International flight attendants, which was equal to 0.384, but this correlation was a weak uphill (positive) linear relationship. As a result, the present study suggests that Thai aviation companies should be aware of using the TOEIC as a recruitment requirement. To ensure a more accurate determination of language proficiency of applicants, it is recommended that the Thai aviation industry develop their own English language proficiency test for staff recruitment processes.