Southwest sells BWI-CLE one-way tickets for about $90-93 advance purchase WGA, and about $200 for a two day out one-way WGA ticket. Both include checked bags and ability to change without fees.

I can't see Frontier wanting to directly compete on that one, since Southwest would just add capacity and discount the fares, but maybe Frontier could on BWI-YNG and sell tickets for about $50-60 Economy advance purchase (2-3 weeks out). This would be ideal for those willing to drive a little to save some money on fares.

It can offer a BWI-YNG-MDW itinery and sell $60 tickets on the YNG-MDW sector as well. That second sector could be really popular for people from Pittsburgh seeking low fares to Chicago and vice versa. I came up with $60 as that's the fare on TTN-CLE currently 3 weeks out, and it's roughly the same distance.

In my opinion, Cleveland to Chicago is too close of a distance for a leisure/low fare carrier, although F9 now has a growing presence in both CLE and MDW. MegaBus covers that route. I've driven it a couple of times and found it's straightforward ride on Indiana and Ohio turnpikes. I once rented a car at MDW that had an Indiana I-PASS tag that I paid a daily fee, but it covered all tolls during my rental. It came out to a lot less than the actual tolls of crossing states. I think Pittsburgh being 2-2.5 hours extra however makes the drive a little too long, so YNG being somewhat straddled between CLE and PIT might be a good airport for F9 as well, even though F9 is already in CLE and has international service out of PIT.