JetBlue would scrap the Spirit brand if it buys the airline and leave Frontier as the only large ultra low-cost carrier in the US

A $3.6 billion bid for low-cost giant Spirit Airlines has been placed by JetBlue Airways, with plans to scrap the brand.

In a press release, the airline confirmed the offer and called it "unsolicited." Frontier Airlines announced in February that it would buy the airline for $2.9 billion.

The combined carrier would be worth an estimated $6 billion, which is less than the $7.3 billion that JetBlue is rumored to be worth.

According to CNBC, the news has puzzled Wall Street analysts, with Bank of America analysts writing that they struggle to find additional benefits for JetBlue.

Financial firm UBS was confused and called the bid a "headscratcher".

If the budget carrier accepts the offer, the budget carrier will lose its yellow-plane brand and have its jets wrapped in blue. Frontier is the only large low-cost airline in the US, according to analysts.

The founder of the Cranky Flier travel website told CNBC that Frontier doesn't have a serious competitor anymore.

According to the New York Times, the carrier may not see as many benefits as Frontier. Ultra-low-cost carriers like Frontier and Spirit charge extra for things like bags and food.

There is a more premium product that offers free onboard wi-fi and inflight entertainment.

The acquisition is a growth opportunity, despite the product differences.

He said in a press release that the transaction would create sustained, long-term value for the stakeholders in both companies.

The acquisition would allow for the growth of the fleet. According to CNBC, if the merger goes through, they will have 670 planes by the year 2027.

The merger would help the airline grow in places like Dallas/Fort Worth, Chicago O'Hare, Atlanta, and cities in Florida, according to the executives. The two airlines overlap on 9% of the routes.

Frontier told Insider that the timing of the offer was surprising due to its ongoing lawsuit over its Northeast alliance with American but that the merger of the two airlines would be synergistic.

The approval odds are unknown. Some members of Congress, like Senators Elizabeth Warren of Massachusetts and Bernie sanders of Vermont, wrote a letter in March saying they were concerned that the combined company could impact customers by increasing fares and worse customer service. The US Department of Justice has not commented on the bid.