The primary owner of Sun Country Airlines Holdings Inc. is looking to reduce its stake by around 15% just two months after taking the airline public.

In a filing with securities regulators late Monday, Sun Country said Apollo Global Management, the New York private-equity firm that has owned the airline since 2018, is planning a secondary offering that would leave it with 61.1% ownership.

Rather than be reinvested in the airline — like the funds raised during the company's initial public offering in March — the proceeds from the sale will go directly in the coffers of Apollo's investment funds.

The offering includes an optional sale for Apollo and certain underwriters that could further reduce Apollo's stake to 59.5%.

In all, the offering would place up to 6.9 million more of Sun Country's 57.1 million shares with the public. Based on Monday's closing stock price of $39.74, that would yield $274 million to Apollo before commissions and fees.

However, news of the offering sent Sun Country shares down 10% to around $35.50 in early trading Tuesday.

A spokeswoman for the airline deferred comment to Apollo, calling it "their news." A spokesman for Apollo declined to comment.

Twin Cities-based Sun Country raised $218.2 million during its IPO, exceeding expectations. The company's stock has wobbled between $37 and $42 per share for the last month, well above its listing price of $24.

Executives at Sun Country, which caters to Midwesterners taking vacations, have been upbeat on leisure travel demand returning as the pandemic subsides. Investors also like the airline's alternative revenue streams: a large cargo contract with Inc. and a charter business the serves sports teams, military personnel and casino clients.

Apollo bought Sun Country for about $188 million in April 2018 and has invested more than $200 million on fleet and technology upgrades, according to public filings.