Worst pax ever?

The phantom.

"Back in the day" I was flying a light jet. Most legs around 1.5 hours - no one ever used the loo (really just a bucket full of blue water). On the _extremely_ rare occasion when they did, it was easy to tell - they'd make a big deal of closing the doors and curtains that partitioned off the lav - you knew, and
1) They usually had the courtesy to tell you, so you could dump it, and
2) It was NEVER used for, shall we say, number two.

(I'm sure you can see where this is going)

Yes, some phantom $h!++#r managed to discretely plop him (or her) self down on the dunny, evacuate their bowels, and slip back to their seat undetected. This in and of itself wouldn't have been so bad - but as previously mentioned, the facilities were rarely used, and when they were we always knew (or so we thought).

(As a side note, the lid to the potty seat apparently makes a surprisingly effective seal)

Fast forward, oh I'm guessing somewhere between one and six months. It's time for some routine maintenance and general housekeeping on the old bird. So we decide to dump the old (and as far as we knew, unused) blue juice and put some fresh in.

It took approximately 1.5 seconds for the stench from the now thoroughly fermented fecal matter to pervade the entire aircraft. Mere words cannot describe what greeted my colleague and I - a thousand rotting possums, a paper mill, and an oil refinery all together would have been pleasant by comparison. We beat a hasty retreat out of both the aircraft and the hangar, fresh air being a prized commodity at that juncture.

Eventually we managed to dump the reeking contents of the bucket, but even with repeated rising with hot water and fresh blue juice we never quite got the stink out of that bucket. It took a good two days airing out before the airplane itself was passable - with the help of a healthy dose of Ozium.

So where ever you are Phantom $h!++#r, you will live forever in my memory (and my damaged sinuses).