Originally Posted by Yaatri

For interlined tickets, DL will continue to check your bags through. MITA governs multilateral interline traffic arrangements. It defines liabilities and responsibilities. Separate tickets do not have MITA protection.
Airlines checked your bags through to the final destinantion even if you were flying the final leg with a different airline using a different ticket, which was not conjuncted, as a courtesy. As its use grew beyond occasional incidences, it was destined to die.
This is something people should remeber. Excessive use of a courtesy or privilege can kill it. Or when every on tries to avail of a courtesy, it turns into a chaos.