While purchasing the first ticket, you can mark the Return button, or after purchasing one-way, you can re-enter the system and purchase the return tickets by examining the reverse route sign with the reverse route sign.
When you search for flights between Dallas and Nashville, all active companies and flight times on the date you entered are listed. You can find the cheapest flight tickets by sorting this list by price.
The most frequently used airline companies from Dallas to Nashville are generally
Finnair,
Japan Airlines,
Alaska Airlines,
Gulf Air,
American Airlines,
British Airways,
Sun Country
are companies.