I am trying to book AUS-AUA on CO.com and there are three main routings, AUS-IAH-AUA, AUS-EWR-AUA, and AUS-ATL-AUA (DL).

When looking at AUS-ATL-AUA flight, it shows the first half as being available only in Economy, even though I am searching for First. Going to the DL website and trying the same thing, I get the same routing all in first for the same price as on CO.com.

I can't figure out if CO.com is assuming that "R" class on DL is First or what.

The other strange anomaly with this whole thing is that the return is only available on DL.com through JFK, whereas the DL return on CO.com shows the ATL routing.

Should I book the tickets and call CO.com support or will they even be able to do anything if half of the ticket is on DL?