Well, that's a new one.
This is all the flight info on ExpertFlyer says about yesterday's US719:
0719/28DEC
P FCO/OUT 1132A E00:03 *N271AY*
P FCO/OFF 1151A *N271AY*
P PHL/ON 332P *N271AY*
P PHL/IN 335P E00:10 *N271AY*
P PHL/OUT 603P L00:03 *N655AW*
P PHL/OFF 637P *N655AW*
P MCI/ON 835P *N655AW*
P MCI/IN 839P *N655AW*
P MCI/OUT 933P *N655AW*
P MCI/OFF 946P *N655AW*☨
P MCI/OFF 946P *N655AW*
P SFO/ON 1125P *N650AW*
P SFO/IN 1136P L02:10 *N650AW*
SKED FCO ORIG 1135A GTD G5 SHIP 271
PHL 345P 600P GTA A25 GTD C20 SHIP 655
SFO 926P TERM GTA 23
So it was on the ground for 1 hour, 11 minutes in Kansas City. This flight also diverted to MCI today with a different A320 (N650AW), presumably for the same reason, but was on the ground for 59 minutes:
0719/29DEC
P FCO/OUT 1131A E00:04 *N272AY*
P FCO/OFF 1153A *N272AY*
P PHL/ON 307P *N272AY*
P PHL/IN 310P E00:35 *N272AY*
P PHL/OUT 600P ONTIME *N650AW*
P PHL/OFF 613P *N650AW*
P MCI/ON 804P *N650AW*
P MCI/IN 811P *N650AW*
P MCI/OUT 850P *N650AW*
P MCI/OFF 903P *N650AW*☨
P MCI/OFF 903P *N650AW*
P SFO/ETA 1104P L01:38 *N650AW*
SKED FCO ORIG 1135A GTD G5 SHIP 272
PHL 345P 600P GTA A26 GTD C30 SHIP 650
SFO 926P TERM GTA 26
They are retiring many of the older A320s that occasionally have winter headwind issues and replacing them with newer A321s that very rarely have to make such stops.