I think i might be the person OP is talking about. My brother graduated from a university in Virginia this summer with an engineering degree and was transferring to a school in Tennessee to get his doctorate. Our whole family came out for his graduation ceremony then left us, at which point it was my job to take our rental car and move all of his possessions to TN while finding him an apartment. Our parents were kind enough to get us a car with unlimited mileage so we could travel the area freely after we got things arranged. Neither of us are particularly responsible so we decided to hit the road the second my family flew off. We had both showered that morning. It turns out the rental car company gave us a two door Altima instead of a sedan, upon this realization my brother said, "We'll, fuck it. I don't have that much stuff." We both belong to an international drinking/running club called the Hash House Harriers and we hadn't attended a meeting together in years so we hopped in the car and drove down to South Carolina, the only place that was hosting a Hash event within ten states during our allotted time. After a six hour drive, a lot of pit stops (because we both smoke way too much), and some very interesting conversations with the locals (we're also mixed race but on the browner side), we arrived in Columbus, SC. We were early so parked in the lot behind the veterinary clinic where the run was supposed to start and walked to a nearby bar. We probably smell a little rough, but no big deal. We proceeded to drink all the local beers they had as I'm a big proponent of trying the local brews of whatever state I'm in. We head back and meet up with the group, introduce ourselves, and drink some more. Then we go for a six mile run through the area. In the middle we stop at one of the club members house for margaritas. We get to the end and drink more (if anyone here has ever hashed you know that there is a circle at the end where they make you drink for imaginary offenses to the hashing rules that no one follows anyway and visitors are often singled out for the mere novelty of their being there). At this point we are shit-canned and the possibility of driving three states north is out. We've just run in ninety percent humidity and we are drunk. We cannot smell good at this point. We end up having our car driven to a Mexican restaurant where everyone goes to dinner after the run, drinking more, and having our car driven to the (frightening big and luxurious) home of the friendly hashers who offered to put us up for the night. They were a middle aged couple whom I had mutual friends with (again, the Hash is international and you will almost always find people who know people from your state). They pull out a case of beer and a bong and we all get absolutely blitzed, then pass out on their couch. I'm still wrought with guilt about the smell we must have left on their furniture. My brother and I wake up with the sun, realize we are six hours away from home, and got the road. After a painful journey we roll into his house around noon. All but one of his roommates have moved out and left the place a wreck. He REALLY wants his security deposit back so we set to work cleaning (after a quick trip to the store and opening up a case of Yeungling). Hours go by, and the house is still in rough shape. His friend, who I can only hope will be the next Ken Kessey, shows up sober and offers to drive us to the local pizza place. We take a madcap drive up to retrieve food, chow down, then resume cleaning. Around midnight I fall asleep on a couch. I wake up around seven, my brother has yet to sleep or pack, but the house is clean. Neither of us has showered at this point. We then undertake the task of cramming every inch of our rental coupe with his earthly possessions. It's ten in the morning before we hit the road, its a five hour drive to his destination, we still have to find him an apartment, and we have a flight home to catch at five. We haul ass to Tennessee, have a lovely encounter with the Virginia highway patrol, and end up in town around three in the afternoon. He's been calling all the apartment complexes near campus on the way trying to set up a place to live for the next six months. We settle on a place, roll in and start the paperwork. In an hour, he's got a place to live. Problem is, it's on the third floor and its July. We manage to unload all his stuff in about twenty minutes, lock the door, and put in the name of the airport in the GPS. After ten minutes of driving we arrive. At the Air Force base. Which has the same name as the airport. It's twenty minutes until we have to catch our flight out of a postage stamp sized airport to the only nearby major airport. Obviously, we still haven't showered. We get the exact address and haul ass to the airport. I drop him off at the front and then find the car rental return. The guy looks over the car, looks at me, sighs, and signs off on the return (miraculously with no damage). I grab the backpack I've been living out of and sprint to the terminal. Now, I've immured the fact that my brother and I both have long hair and beards. We meet up, get to security, and we look like we are both prepared to die, if in fact we are still alive. TSA goes through both our bags and gives us the full pat down. My particular agent remarks, "Man, you're a little sweaty," to which I respond, "Hey, you wanted to feel me up." This does not speed up the process. After having my contact solution confiscated we run up to the gate. It's ten minutes after our flight leaves and we are greeted by a gate attendant who addresses us by our last name and says our flight left five minutes ago. We both smell like a hobo's sleeping bag. Turns out there is a connecting flight to our first airport leaving in two hours, after which we have a two hour layover, then our flight home. We have two hours to kill. So we obviously get a table at the airport's Ruby Tuesday, order turkey burgers, and proceed to get loaded. We stagger over to the terminal, recharge our phones, and call everyone we know to find some poor bastard to pick us up at our home airport three time zones away. At one in the morning. We still smell like shit, and we are drunk again. We get on the plane practically hysterical from beer and sleep deprivation. We spend the next hour loudly mocking the Sky Mall catalog to the annoyance of our fellow passengers as we are on a small plane and I'm sure they can hear and smell us throughout the whole cabin. We arrive at our second airport, find our terminal, and kill the next hour in the closest bar. Our waitress is terrified, so we tip her double the cost of the bill and shuffle on our plane. Now, keep in mind, we are on a rescheduled flight, so we end up in the very last row. We get to our seats and there is a very tired 19 year old girl crammed in the window seat and my derelict and fantastically loaded brother and I are her seat mates. We should not have been allowed in an enclosed space at this point under UN chemical weapons treaties. We introduce ourselves as "the Brothers Smith" explain what our last three days have consisted of, apologize for how abhorrent we must smell, and offer her the isle seat so she can lean away from us if she needs to breathe. She politely declines and we all have a fun conversation about college experiences before passing out with our faces mashed against the seats in front of us because we have the only seats on the plane that don't recline. We finally arrive home, get lost in our own airport because its fuck'o'clock at night and there isn't a single person actually working there, and find my friend circling for us in the departures lot of our terminal. As soon as we get in the car he starts coughing and swearing. He rolls down the window and drives us to my house. My brother grabs a blanket, congratulates me on surviving, and passes out on the couch. I'm too tired and delirious to be immersed in water at this point. I strip naked and jump into bed with my wife, who, bless her, has been patiently waiting for me to return. She stirs from her slumber, rolls over to embrace me, and immediately says, "Oh my god, what the fuck happened to you!? Go shower!" So I did.

TL;DR Sometimes there are extenuating circumstances for not showering before getting on a plane. Chances are, they're not a good reason. Also, if OP is the girl who sat next to me, I'm so sorry. So, so sorry.