After years of legal challenges and delays, Hartsfield-Jackson International Airport is rebidding its advertising contract.

Clear Channel Airports has held the contract for advertising at the Atlanta airport since 2002. But Corey Airport Services, which lost out in the competition for the contract, filed a federal suit in 2004 claiming the city and the airport steered the contract to a competitor with political connections.

The city of Atlanta in 2011 struck a $3.9 million settlement with Corey, a deal the airport had said made it clearer that it could move forward and rebid the contract. In 2012, Corey lost an appeal in its case against Clear Channel and its minority partner. Meanwhile, Clear Channel has held the contract on a month-to-month basis.

Now, the airport is rebidding the contract through a bidding process.

On Wednesday, four companies threw their hats into the ring to be pre-qualified as bidders for the contract at the world’s busiest airport: Clear Channel, Corey Airport Services, JCDecaux and Titan. After bids are submitted, the airport plans to award a contract by the end of the year.