Regulators are reportedly looking to block the prospective merger between JetBlue Airways (NASDAQ:JBLU) and Spirit Airlines (NYSE:SAVE), sending shares of the latter sliding.

Both the Department of Transportation and Department of Justice are looking to halt the deal on the grounds that the merger would be anti-competitive, according to Bloomberg.

Per prior media reports, executives from the carriers met with the DOJ in late February in a "last-rites" meeting to assuage regulatory concerns on the planned merger. That meeting followed reports earlier in Februarythat the department was planning to file a suit as early as this month. Per the latest reports, the efforts to shift the DOJ’s stance on the deal were unsuccessful as a suit is indeed due to be filed as soon as Tuesday.

Citing people familiar with the matter, Bloomberg also indicated that the Department of Transportation will launch a parallel proceeding to “block the transfer of Spirit’s airline certificate as incompatible with the public interest.” This is a power the agency hasn’t used since the deregulation of the industry under the Carter administration.

Shares of JetBlue Airways (JBLU) rose 2.22% in afternoon trading while Spirit Airlines (SAVE) stock slumped over 9%before rebounding modestly.