Southwest will add Nashville red-eye flights as part of shakeup

Why it matters: The changes come the same day the airline reported second-quarter results that beat some expectations following a bump from a summer travel boom but still "fell short" in other key areas.

How it works: Over its 50-year history, Southwest has had an open seat model, with passengers only assigned a boarding group and a number that represents a reserved spot within that group.

• The airline said its research found 80% of its customers and 86% of potential customers preferred assigned seating.
• "When a Customer elects to stop flying with Southwest and chooses a competitor, open seating is cited as the number one reason for the change," it said.
• The company didn't specify when the changes would go into effect but said it would provide more details in late September.

Zoom in: Nashville is also among five markets where Southwest will begin offering overnight red-eye flights.

Go deeper: Read Knutson's full story about Southwest's "transformational change."