Sorry no. No matter what your rank is in real life, FsPassengers remains a game. You need
to make your way through the normal progression. Allowing people to start at
C4 would be unfair to those that worked hard to reach their level without any cheats.

I recall that you don't need to start a company with 'career mode' set which
limits you to some aircraft. You can fly even a 747 at C0 given that you have
set a company without the 'career mode' (which is optional and disabled by default)