There's much more to running an airport than airlines and airliners. There are millions of customers, hundreds of suppliers, quite a few competitors (usually), annoying government officials and basically anything you can think of.
Therefore, there's a great need for both marketing specialists and PR
people at airports.
staff is in charge of all press relations, issuing press reports, special announcements and dealing with special occasions - both good and bad (good being celebration of a new terminal, and bad being malfunctions and disasters of all sorts).
Marketing personnel would concentrate on making the airport as profitable as possible. Although we may not see airports as "businesses", they actually are, and must be operated as such - even if they're government owned. Marketing an airport, you'll negotiate advertising campaigns, sell advertising spots within the airports, lease business areas for shops and services, launch special deals, cooperate with airlines and so on. Basically, you'll do anything possible to achieve your goals, and much more. Try being as creative and open minded as possible and yet realistic and cautious.