Pros
Smart and fun people to work with - you can make friends easily and learn from your colleagues a lot. You can always express your opinion and ideas, and the culture is much more open in comparison to large corporations. As the company is small, you get a lot of responsibility and client exposure (if you want it) from the beginning. The team is young, diverse and never boring. It is nice to know that your work helps to solve real-world problems, affecting people everyday, i.e. improving the experience of passengers with accessibility needs etc.
Cons
It's a startup, so you never know what is going to happen - the priorities might change, so you have to be able to adapt quickly and be ready for surprises. It is not suitable for people who prefer a stable highly structured environment. There is no formal training, you have to learn on the job and take ownership for your work from the first week.