United Airlines CFO Andrew Levy has resigned, effective immediately, and the Chicago-based airline said it has started a search for a replacement.

No explanation was given for the surprise move, which United revealed May 17. SVP-finance Gerry Laderman will serve as acting CFO.

Levy, who was formerly the president of Allegiant Air, joined United management as CFO in August 2016 at the same time as Scott Kirby—who jumped from being president of American Airlines to being United’s president. CEO Oscar Munoz said at the time he was bringing together what he called a “dream team” of senior managers. Both Kirby and Levy were widely seen as potential future airline CEOs.

Munoz said in a brief statement that Levy “leaves the company in a stronger financial position and with a clear strategy and framework in place,” adding: “Our exceptional operational performance and our focus on productivity are driving improved profitability despite anticipated fuel headwinds and we remain confident in our existing financial guidance.”

Levy sent a separate statement to reporters. “I can confirm I resigned the position of [United CFO] on Monday, May 14,” he said. “Since my arrival in August 2016, the company has faced several challenges, but we have nevertheless enjoyed success. As satisfying as this job has been, I am considering several exciting opportunities and will choose one in the coming weeks.”

Levy said he will continue to serve on the board of Panama-based Copa Holdings.

United earned a $147 million net profit in the 2018 first quarter, up 48.5% over $99 million in net income in the 2017 first quarter.

Aaron Karp/Aviation Daily, aaron.karp@informa.com