By David Shepardson

(Reuters) – Spirit Airlines (NYSE:) JetBlue Airlines demanded that shareholders reject its hostile offer for merger. It claimed it was a “cynical attempt” to discredit the company’s merger with Frontier.

JetBlue believes its $30 per-share offer surpasses Frontier’s cash-and stock deal. Regulatory concerns should not be a reason for JetBlue to withdraw its bid. Frontier’s offer valued Spirit at $20.18 by shareholders will be up for a vote by shareholders on June 10.

JetBlue disclosed Monday that it had been considering acquiring Spirit for years. Spirit also questioned JetBlue’s assertion that an agreement could not be reached due to antitrust concerns.

JetBlue offered $33 per share in April and argued that a deal would help it compete better with the four “Big Four” U.S. carriers, who control almost 80% of the passengers market.

JetBlue, the sixth-largest U.S. passenger airline, would manage Spirit under its JetBlue brand. However, it promised to pay a reverse breakup fee of $200 million or $1.80 for each Spirit share if the deal was not approved by antitrust authorities.

JetBlue acknowledged that the possibility of a DOJ lawsuit to prevent the merger being completed was 100% certain during extensive talks between Spirit, JetBlue and JetBlue. JetBlue must prevail (which is contrary to DOJ’s enforcement approach) to complete its acquisition of Spirit, Spirit explained in a statement.

JetBlue declined to comment immediately on Thursday.

JetBlue sent a Monday letter to Spirit shareholders, offering $30 per share. It also stated that it is ready to negotiate in good faith an agreement at $33, but subject to the receipt of necessary diligence.

Spirit stated that JetBlue’s attention on Spirit was an attempt to ignore the fact JetBlue’s business is in serious trouble. Spirit also said that JetBlue’s stock had dropped 34% from March 29.

Spirit said that “JetBlue stockholders clearly agree that Spirit’s quxotic offer by their company is a dead end and posing significant risks to their business,” Spirit continued.