No-frills, budget airlines often lead the industry in customer complaints, according to government data, so if one were to disappear would it be missed by travelers? That is a question U.S. regulators will be asking after Frontier Airlines said Wednesday that it wanted to buy Spirit Airlines,

Frontier said in a release that it has met with Spirit’s board and executives since it made its proposal this month.

Spirit, which filed for bankruptcy protection last year, says it has rejected the new Frontier overture but would be open to a higher offer.