I did a search and didn't see anything about this. I know for 20+ years Delta issued FF/SM numbers that started with a 2 and were 10 digits (in my family we have numbers starting with 208, 217, 229, 255). And I've heard the early DL FF numbers started with a zero, and the carried over Pan Am ones started with 4000.

Today I enrolled two children in SM, and both got 10-digit numbers that start with 930. Anybody know when DL ended the 2 series and went to 9? I created an account for someone right around the time of the merger, and I recall it was still a 2-series number. Was this something that came from NW after the merger? Just curious.