Fair point. Although B6 dropped the MSP-BOS route and SLC-BOS only operates for a limited seasonal schedule. So I wouldn't consider those competitive routes. While DL is not currently matching B6 cheapest fares on DTW-BOS, it does have some targeted one-way fares starting at $149 BE/$184 Main which are aligned to the B6 flight timings. One-way DL fares on DTW-BOS that don't fit flight timing windows below start at $249 BE/$284 Main.






One thing I neglected to mention is there are some routes where the legacies have "Accompanied Travel" fares where there are cheaper fares available if booking for 2 or more people on same reservation. The BOS-TYS route mentioned above happens to be one of those routes. These fares have a '9' in second position of fare basis code on DL fares and have an "Accompanied Travel" section in the fare rules. The cheapest one-way Main base fare for one passenger on date below is $254.12, while if 2 or more are booked on same reservation, there is a $148.08 one-way Main base fare available for booking. If you attempt to split res after booking down to a single ticket on one res, presumably a refare will be involved.