DL, along with UA & AA, as well as several non-US carriers, use the same anti-fraud vendor which runs purchases through an algorithm and identifies purchases with a high fraud potential.

The algorithm is, of course, proprietary and particularly sensitive because if the "bad guys" knew exactly what it was, they would figure out how to evade it.

Nonetheless, tickets to and originating in high-fraud zones are big red flags. Add a couple of other data points and you are in the jackpot.

Doesn't make you a fraud, just means that there is a risk which DL is not prepared to take. Because DL and possibly others, but not the customer, bear 100% of the fraud risk with a CC, that's the solution.

I am surprised that DL will not permit you to submit copies of the relevant documents in advance as other carriers do, although it is often from a business email account where the carrier can verify an IP address.