On Tuesday, the U.S. Department of Transportation approved the proposed deal between US Airways and Delta that involves trading takeoff and landing slots at capacity restricted LaGuardia in New York City and Washington, Reagan National Airport. This is a transaction that would significantly impact both airline’s operations and by extension, where you can fly to from CLT.

That though isn’t the end of the matter. The Antitrust Division of the Department of Justice also must approve and it hasn’t yet. In fact, it put out a press release just after the DOT said “yes” stating:

The Antitrust Division has been conducting an investigation of US Airways’ acquisition of Delta Airlines’ slots at Washington’s Ronald Reagan National Airport to determine the transaction’s impact on competition and traveling consumers. The division will continue its investigation with a focus on the increase in US Airways’ share and use of slots at Reagan National and the resulting decrease in Delta’s share of slots at this slot-constrained airport, at which passengers pay among the highest fares in the country. The division will not continue to investigate the acquisition of slots at New York’s LaGuardia Airport because the division has concluded that acquisition does not raise competitive concerns.

While the Antitrust Division works closely with DOT on airline issues, the two agencies act under substantially different statutory and regulatory frameworks. The role of the Antitrust Division is to protect competition and to ensure that companies do not raise prices to harm consumers in violation of the antitrust laws. Under the antitrust laws, the division can and will take appropriate action, if warranted, at the conclusion of its investigation.

Which is kind of interesting, given that US Airways, Delta, DOT, and DOJ spent months negotiating the current version of the slot deal after the DOT objected to the original prposal.