This study examines the frequency and the functions of code switching in informal conversations among Jordanian pilots, who have created their own jargon. It also explores the most frequent English expressions that the pilots switch to in their informal Arabic discourse. The conversations of eight Jordanian pilots aged between thirty and fifty-five were tape-recorded in three separate informal natural settings. The data were used for the purpose of finding out what the pragmatic and communicative functions are that the pilots' code switching serves, and to investigate the most frequent expressions used in their conversations. The results showed that eight main conversational functions can be identified in their code-switching routines, namely: to compensate for the lack of exact equivalents in Arabic, to avoid interruption to the communication when not knowing the Arabic equivalent, to replace long and technical terminology in Arabic with acronyms in English (acronyms are not common in Arabic), to use aviation titles and ranks, to quote/ directly report phrases of speakers, to say the numbers, to refer to names of companies, places, documents, and organizations, and to insert some English formulaic expressions. The findings also showed that the most frequent terms and expressions used in code switching amongst Jordanian pilots are more related to the aviation register than to common-core vocabulary.