Originally Posted by knope2001

Just look at the IND-DEN flight times in comparison to the DEN-JAC flight times and you'll see the issue.

Starting June 12 IND-DEN runs twice daily, and most days the flights arrive Denver at about 4:15pm and 8:10pm, but the DEN-JAC flight leaves Denver at 3:45pm. The return doesn't work either -- the flight from JAC arrived DEN at 7:05pm, but the DEN-IND flights leave Denver at 10:30am and 2:30pm.

Frontier generally seems to be focusing more on local traffic over connections, which means somewhat fewer frequencies and flights not as timed for connections. That means some city pairs won't exist that used to.