Delta does not have bitters on board. And as
BSBD said, most bartenders screw up an Old Fashioned, so I'm not going to trust a flight attendant to do it. In the air, I'm fine getting Woodford refills.
Actually, though, my fiancee recently got the
carry on cocktail kit for me, and it's pretty cool. Comes with a classy napkin, makes two drinks. Not half bad at altitude.