Spiff is correct.

The only problem with your hypothetical plan would be if (for example), your first flight of the day was delayed to the extent that you couldn't make your second flight. Since the flights are on separate tickets, DL has no responsibility to accommodate you on the next flight from ATL to BOS.

Note that the reason your itinerary works is because you are not circumventing any fare rules, such as minimum stay.

A portion of Delta's ticketing policy:

Rule 100G
… a ticket is invalid: … if Delta Air Lines determines that the ticket has been purchased or used in a manner designed to circumvent applicable fare rules. Delta Air Lines specifically prohibits the practices commonly known as: … "BACK TO BACK TICKETING" - The combination of two or more round-trip excursion fares end to end for the purpose of circumventing minimum stay requirements … Where a ticket is invalidated as the result of the passenger’s non-compliance with any term or condition of sale, Delta Air Lines has the right in its sole discretion to: Cancel any remaining portion of the passenger’s itinerary, Confiscate unused flight coupons, Refuse to board the passenger or check the passenger’s baggage, or Assess the passenger for the reasonable remaining value of the ticket, which shall be no less than the difference between the fare actually paid and the lowest fare applicable to the passenger’s actual itinerary.

I tried to add a link here, but it (from thewww.onetravel.com "Rules of the Air") was so long, it didn't work.

[This message has been edited by Dave M (edited 10-09-2001).]