In response to the above enquiry.
One explanation is that being seated for a relatively long period of time in an airplane seat, especially in an economy class seat on a long flight, the bladder and the prostate are being compressed by the lack of sufficient leg room.
One does not really relax well on board a flight sitting in an economy class seat. Mentally and physically, there is always a slightly conscious feeling of anxiety. Physically, the muscles tend to tighten up a bit during flight. And somewhat subconsciously, one tightens the bladder muscles to control the bladder.
Restricted leg movements also make the muscles tighter than usual. This also explains the onset of edema in the ankles, feet and knees during flight. Bodily fluids accumulate.
The day after the flight, and after getting over jet lag, one begins to relax physically and psychologically, the muscles relax, and this muscle relaxation releases the grip on the bladder during flight. Without the grip on the bladder, urination would be more frequent.