The X-ray screening task is one of the most critical parts of the security processes at airports. Improving this task is related to the knowledge of the screeners directly. This paper describes an investigation on real-time knowledge transition during security screeners' performance of the x-ray screening task at the airports. Using eye-tracking glasses, behaviours of 10 x-ray screeners, including novices and experts, were observed during the regular screening task. Results show that there is a direct relationship between expertise and the amount of knowledge gained by and transferred to security employees. Experts demonstrated a superior ability to transfer knowledge to other security employees than novices. Given the evidence of real-time knowledge transition that occurs during the screening task, this research proposed an intelligent interface to better facilitate the process of real-time knowledge transition. The interface should assist novices' learning process and their faster transition to becoming experts.