Maximum Ride are YA books by James Patterson, the prolific murder-mysteries-for-moms author. They start off decent and go downhill a bit, but anyway.

The protagonists are kids who got genetically engineered or something into bird people. (Like typical angels, not like the Aarococra from D&D) they fly around and try not to get caught. I feel like there’s some similarity in the personalities that would be fun to read in a crossover fanfic.