The short term car parkings are buggy, they generate too much private car traffic with sims, who doesn’t use the airport. Remove some of them and build some more car-/bus-/taxi-stops. Sims, who use these are real airport visitors/users.
A long time ago the problem was discussed here: Airport CEO or Parking Lot CEO? - #19 by djr5899. As you see in the example, reducing the short term parking lots reduces only the sims, who do not use the airport. You’ve got still enough lots for the real visitors.