I was returning from a business trip on a bus, travelling from a remote town in my state back to the city. There were very few people on the bus and they were all seated near the front, so I sat up the back by myself.
After about half an hour I started to get a bit of a hard on, and as it grew it started to hurt a bit. I shuffled it into a better position, and just doing that felt pretty good, so I stroked it through my shorts for a minute. That felt even better and made me want to do it all the more.
I looked around and there was still no one anywhere near me, so I pulled the leg of my shorts across and got my cock out. It looked really good sticking out of my shorts, and I could feel a slight breeze on it from the air conditioning.
I grabbed it and stroked for a few seconds, but suddenly I felt like I was going to cum. I didn't quite know what to do so I stopped and waited for the feeling to die down a bit, but it didn't, and I knew if I touched it again I was going to cum.
I looked in the pocket of the seat in front of me for a tissue, or something to wipe up the cum, but all I found was a sick bag. It was not what I was hoping for but it would have to do. I opened it out and moved forwards on the seat and held it under my cock; then I grabbed it and jerked it and squirted my load into the bag.
It was huge and it seemed to go on forever, but when it was finally over I put the bag back into the seat in front of me, and just sat there with my cock out until the residual cum ran out of me. Then I slept for most of the trip.
That was one of my favourites, and I still jerk off when I think about that trip.