Is Gryffwing Cavalry legal in Standard, Modern, and Commander?

Gryffwing Cavalry is legal in: Modern, Pioneer, Legacy, Vintage, Commander, Historic.

Gryffwing Cavalry

Q: What type of card is Gryffwing Cavalry?

Gryffwing Cavalry is a Creature — Human Knight. Its oracle text reads: "Flying Training (Whenever this creature attacks with another creature with greater power, put a +1/+1 counter on this creature.) Whenever this creature attacks, you may pay {1}{W}. If you do, target attacking creature without flying gains flying until end of turn."