I have gone through the online schedules of AA, DL, and UA, and have tallied up departures by aircraft type for each hub in order to get a picture of how each airline is currently deploying their fleet across their network. This subject has always fascinated me, so the hours of going through schedules are totally worth it

A few notes/disclaimers:
- *This data was collected by hand, so it's possible there are a few inaccuracies. However, I have a high level of confidence in the data.
*Schedules are always subject to change, so the totals from when I collected data may already have changed slightly, and may change further in the coming weeks.
*As we know, the term "hub" is always unavoidably subjective. For the purpose of these threads, I'm classifying a "hub" as a station that has 100+ departures serving 30+ destinations.
*I don't have plans to do this for any other airline's network this summer - if someone would like to make a thread like this for AS, AC, etc., wonderful! Please use 7/23/2018 as the schedule date for a fair comparison.
*For simplicity's sake, I decided not to split out different subfleets in the tallies. International 757-200s will be aggregated with domestic 757-200s, and so on and so forth. I'm also using airline-agnostic aircraft codes, so if a given airline classifies their 737-700s as "73W" (looking at you, DL), the data here will still show "73G" instead.
Enjoy!
ATL
CR2: 119
CR7: 46
CR9: 43
717: 115
M88: 293
M90: 50
319: 5
320: 53
321: 85
73G: 26
738: 25
739: 80
752: 75
753: 8
763: 8
764: 11
332: 1
333: 9
77L: 4
359: 1
Total = 1057
80.3 % mainline
DTW
CR2: 93
CR7: 64
CR9: 90
E70: 6
E75: 4
717: 44
M90: 21
319: 21
320: 14
321: 11
738: 12
739: 32
752: 20
753: 7
763: 3
332: 2
333: 4
359: 5
Total = 453
43.3 % mainline
MSP
CR2: 90
CR7: 38
CR9: 75
717: 43
M90: 48
319: 31
320: 25
321: 16
738: 9
739: 31
752: 28
753: 6
763: 2
333: 3
772: 2
Total = 447
54.6 % mainline
LGA
CR2: 20
CR7: 7
CR9: 80
E70: 35
E75: 56
717: 16
319: 22
320: 22
321: 14
738: 2
739: 1
Total = 275
28.0 % mainline
SLC
CR2: 41
CR7: 14
CR9: 16
E75: 53
717: 15
M90: 11
319: 15
320: 14
321: 18
738: 39
739: 25
752: 7
763: 4
Total = 272
54.4 % mainline
JFK
CR2: 14
CR9: 67
E70: 4
E75: 8
717: 4
319: 12
320: 19
321: 3
738: 9
739: 30
752: 30
763: 10
764: 9
332: 5
333: 8
Total = 232
59.9 % mainline
SEA
E75: 67
717: 16
319: 5
738: 28
739: 23
752: 20
753: 7
763: 5
333: 1
772: 2
Total = 174
61.5 % mainline
LAX
E75: 38
717: 13
319: 10
321: 5
738: 41
739: 16
752: 26
753: 8
763: 5
764: 3
332: 1
772: 1
77L: 2
359: 1
Total = 170
77.6 % mainline
BOS
CR7: 8
CR9: 21
E70: 6
E75: 15
717: 7
M90: 1
319: 6
320: 10
321: 16
738: 8
739: 5
752: 5
763: 3
333: 1
Total = 112
55.4 % mainline