Snowden now "underground" as he failed to show up for his booked Moscow-Havana flight.
Not boarding a plane that has to move through US territory is probably a good move. I doubt the US would do anything, but better safe than sorry. If he has the support of some foreign goverment he should be able to do better than a public Aeroflot flight.
I'm not sure about Snowden now associating himself with Wikileaks though. I'm sure he appreciates the legal and financial help, but Assange has been steadily hacking away at Wikileaks' credibility.