Spirit Airlines (NYSE:SAVE) and Frontier Airlines (NASDAQ:ULCC) announced a $2.9-billion merger Monday that aims to create one of the most competitive low-cost airfares in the U.S. 

The deal will create the nation’s fifth-largest airline, with Frontier Airlines controlling 51.5% of the new company.

“We are thrilled to join forces with Frontier to further democratize air travel. This transaction is centered around creating an aggressive ultra low fare competitor to serve our guests even better, expand career opportunities for our team members and increase competitive pressure, resulting in more consumer-friendly fares for the flying public.” Spirit CEO Ted Christie said in a statement following the announcement. 

There have been exactly 54 airline M&A deals since the inception of the U.S. airline industry. We're going to look at four of the most recent deals to get an idea of what could happen after the merger: