Tax breaks are usually tied to performance measures. A government gives tax breaks for so many dollars invested, or so many jobs created. If the company does not invest or create as they promised, the tax breaks or tax credits can be removed. Often a company will come to the government and want to keep the tax break even though they didn't meet the goals. I, the corporation, didn't meet the goals due to circumstances beyond my control (COVID) but intend to, so don't take away my tax break. Usually governments can renegotiate the tax break giving the corporation a break, but they don't have to. I suspect Delta didn't meet their benchmarks this year.