I know it's a weird question, and sorry if I am not phrasing it correctly, but I wondered whether the relatively short flight times of fighter pilots and contrarily the relatively long flight times of bomber crews made toilet facilities onboard the planes a necessity/ obsolete?
Thanks for all the great answers in this sub, and apologies if I in some way do not stick to the rules of this sub.
Some of them did; most American fighters had a "relief tube", a flexible tube with a funnel at one end that led out of the aircraft. (See e.g. page 12 of the pilot's operating instructions for the Mustang IV: "PILOT'S RELIEF TUBE - The relief tube horn is stowed on a bracket on the floor to the left of the pilot's seat.") They weren't easy to use, though, with layers of clothing and a harness to negotiate, and at high altitude the temperature led to rapid icing:
"To use the relief tube in the P-51 it was necessary to undo the lap belt, unsnap the leg straps of the seat type parachute, then scoot well forward on the seat to use the relief tube, which was a plastic cone attached to a rubber tube which vents overboard out of the belly of the plane." (US 8th Army Air Force Fighter Command USAAF, 1943-45, Martin W. Bowman)
The Spitfire and Hurricane didn't have a relief tube, being designed for short-range interception operations, pilots had to either hold it in or get changed rapidly after landing. Some aircrew had a ritual of urinating right before take-off, often on the tail wheel of their aircraft. Crew of larger aircraft sometimes had alternatives; the Short Sunderland, designed for extended maritime patrols, had a flushing toilet on board. Most RAF bombers had an Elsan chemical toilet, but it was very much a last resort.
For more complete details, believe it or not the Vintage Wings of Canada website has an entire page on the subject: If ya gotta go, ya gotta go: Answering nature's call at 26,000 feet.