As the person responsible for managing and tracking all cargo coming through the airline, you are expected to be a master of the cargo handling software program, to the point where you know the program well and can train other staff on it as well. While you point out how you would rate yourself on your computer skills, talk about prior experiences working on and mastering different software programs. If you have had experience training others on those systems, be sure to bring that up as well. In the end, your interviewer needs to be comfortable with your ability to step into this role and train quickly on the airline's software to hit the ground running upon hire.