Qatar Airways CEO Akbar al Baker says the “ultimate phase” of Doha’s new airport will cost “another $2 billion over the $15.5 billion” already being on spent on the project, in part to accomodate his airline’s aggressive growth, Reuters reports.

Earlier estimates had set the grand total for the three-phase project at $14.5 billion before the airport plans were revised to handle more passengers.

Phase one of the airport is due to be completed later this year, before its initial opening on December 12. Phase two and three are expected to be completed by 2015, although it wouldn’t be fully operational until 2018.