(Reuters) – JetBlue Airways (NASDAQ) Corp’s bid of $3.6 billion for a low-cost carrier Spirit Airlines Wall Street caught unawares by the (NYSE) on Wednesday. Analysts questioned the merits of the merger.

Although both airlines have an Airbus SE-dominated fleet (OTC:), the potential savings will be diminished as JetBlue would have to raise the wages of Spirit pilots who are in a lower band than the rest, Raymond James analyst Savanthi Syth stated in a note.

JetBlue reported Tuesday that they made an unannounced $3.6B bid for Spirit. The offer was at $33 per Share, which could have impeded a $2.7B merger plan between Frontier Group Holdings Inc. Spirit and Frontier Group Holdings Inc.

Spirit stock fell 2.5% to $26.28 beforemarket. That’s well below the offer and suggests investors weren’t confident about the deal. Frontier stock fell 4%, and JetBlue stock dropped 3%.

JetBlue’s management hosts a conference call Wednesday morning at 8 AM ET, where they will discuss more details about the merger.

Frontier and JetBlue want to acquire Spirit, a low-cost airline that they hope will attract more leisure travelers. This will allow them to compete with the legacy U.S. airlines.

Any combination of these two will be subject to close antitrust scrutiny by President Joe Biden’s Administration, who has taken a hard line against any mergers that could reduce competition or increase prices.

JetBlue and American Airlines (NASDAQ) Group Inc have already been sued by the U.S. Department of Justice for their Northeastern Alliance.

Robin Hayes, Chief Executive Officer of JetBlue, stated that he anticipates an aggressive antitrust investigation by the U.S. Justice Department for any Spirit deal. This could extend into 2023.

“We are uncomfortable with the concept (of merging) because the two airlines are concentrated along the East Coast, with substantial operations in Fort Lauderdale. We would also suspect that there will be regulatory resistance,” said Brokerage MKM Partners.