Originally Posted by Efrem
You're in error about DL lifetime miles. Only butt-in-seat miles count toward status there. This became the policy when they introduced SkyMiles in 1995 to replace their earlier Frequent Flyer program. Previously, all miles counted toward lifetime status. They left existing lifetime totals intact when they switched, but since then only flown miles count.
That policy started later than 1995, I'm pretty sure it came into affect on January 1, 1997 (I remember because I became a Delta FF in late 1996 so I received some benefit from this policy before it was dropped).