The main skills I recommend for this job position are interpersonal skills. These include: communication skills (both verbal and non-verbal communication), emotional intelligence, team- work, persuasion, conflict resolution and decision-making. Notice that these are basic to work in any Airline call center since people can call from around the world with diverse situations and conflicts. Hence, the agent should be able to apply these tecniques to get to high productivity.
Also, these are essential to convice the potential client to purchase a ticket with the company, knowing that there is numerous options.