It’s a battle royale between Southwest and American Airlines as they feud over routes to Havana.


American Airlines’ second largest hub in Charlotte, NC, wants to change the route between Charlotte Douglas International Airport and Havana’s José Martí International Airport to depart out of Miami. According to a report from the Charlotte Business Journal, the Charlotte flight is operating at only 55% capacity, leaving each flight about half full. American already has routes out of Miami to Havana.


What sounds like a simple task is actually a headache to undo. Since both airlines were awarded routes, they’re tied to that specific city, meaning an airline can’t shift its route to different U.S. cities to match demand just because it’s not doing well financially. The rules state that American would have to end its CLT-HAV route and compete with other airlines to win another MIA-HAV slot, which there are only 20 nationwide.


That doesn’t mean American didn’t try. The airline asked to be an exception to the rule, petitioning the U.S. Department of Transportation to let airlines determine themselves from what cities to fly to Cuba. “This flexibility would allow American to bring additional benefits to the traveling public while ensuring that all carriers can respond efficiently to further shifts in demand in the US-Cuba market,” AA told the Dallas Business Journal. Southwest had something to say about this logic, writing to the DOT, “in essence, American’s Motion would substitute its own self-interest for the Department’s public interest decisions.”


Southwest ultimately got the DOT on their side, saying that an additional Miami to Havana flight “would not promote competition or diversify our frequency allocations to the same degree as would a second Saturday flight at Tampa, a city that currently has just one daily flight.”


Southwest and American aren’t the only ones in the ring. JetBlue competed for a Havana route from John F. Kennedy Airport when Delta announced it no longer wanted to fly in August. Southwest wanted to add Tampa to the Havana route.