Frontier Airlines — whose owners had wanted to begin public trading of stock by the end of June — reportedly could wait until September or later to launch their IPO, Bloomberg reports.

The Denver-based airline’s parent company, Frontier Group Holdings Inc., filed a registration statement for an IPO on March 31 with the U.S. Securities and Exchange Commission. The plan was for the airline’s owner, Phoenix-based private equity firm Indigo Partners LLC, to trade shares it now owns in the initial…