Join Date: Oct 2000
Location: Munich, Germany
Programs: LH HON, DL FO/MM, Marriott Lifetime Platinum, Accor Lifetime Platinum, Sixt Diamond
Posts: 6,174
You can use DL miles to upgrade from coach (DL fare in Y/B/M class) to business, but you cannot use DL miles to upgrade from business to first.
Only way to do so is to use AF miles.