No initial product is likely to contribute to solving those problems, because most initial products don't lead to anything.
Conversely, a startup that grows sufficiently big can contribute to the solution of almost any problem, including those you mention.
I agree assisting people to reach the airport on-time may morph into a larger corporate vision, but I disagree it's likely to contribute to solving cancer, making better fuel, or reaching strong AI. ...And it's arguably a distraction of rare talent from that calibre of problem.