Originally Posted by
HDQDD
Cost, climate, availability. Usually airlines store stuff in a drier climate, I'm not familiar with KC, but I think usually they go to the desert (i.e. VCV). I suppose with many hundreds (thousands?) of airplanes grounded, you take space where you can get it these days. Also may depend on how long they thought they'd be grounded.
MCI historically hasn't needed both of their N/S runways for regular operations (and even less so with the COVID flight reductions), so presumably the airport authority was shopping the runway/taxiway space to airlines, or Delta approached MCI about deactivating a runway to use for storage.
I do know that Delta has used Jet Midwest (the current operator of the city-owned hangar formerly used by AA/TWA) for A321 induction and mods, so perhaps there was some connection there (Air Canada also uses MCI for heavy MX, and they had some planes parked at MCI as well)