JetBlue Airways Corp. won’t appeal a federal judge’s ruling that declared its alliance with American Airlines Group Inc. violated US antitrust law, and will instead focus on defeating a similar challenge to its pending merger with Spirit Airlines Inc.

The carrier announced its decision in a statement Wednesday three weeks before US District Judge Leo Sorokin is set to announce his final order in the Northeast Alliance case and enter a permanent injunction. While the carriers have sought to save portions of the partnership, US antitrust enforcers want Sorokin to totally dismantle it and block any effort to craft a new “NEA Lite,” according to an earlier document.

“Despite our deep conviction in the pro-competitive benefits of the NEA, after much consideration, JetBlue has made the difficult decision not to appeal the court’s determination that the NEA cannot continue as currently crafted, and has instead initiated the termination of the NEA,” JetBlue said in the statement. The carrier said it would start a process of winding down the alliance with American “over the coming months.”

American Air has said that it intends to appear the court ruling. The carrier had no immediate comment on JetBlue’s decision.

Shares of JetBlue and American were little changed in postmarket trading. Spirit rose 2.7% as of 4:19 p.m. in New York.

JetBlue has opted to concentrate on saving its planned $3.8 billion combination with Spirit, which has also been challenged for allegedly violating antitrust statutes. Gaining Spirit — the largest ultra discount carrier — is the only way it can gain the size and heft to compete with larger carriers that dominate the US market, JetBlue has said. An Oct. 16 trial date has been set in that case.

Read more: JetBlue, American Offer to Rework Alliance After Legal Setback