The two nearest airports are Tongren Airport and Zhangjiajie Airport. It takes around 1 hour from Tongren Airport to Fenghuang Town. From Zhangjiajie Airport, you need spend around 4 hours. But I am not sure that there are international flights to these two airports. Changsha Huanghua Airport is an international airport. Maybe, you can get there first and then change flights to Tongren or Zhangjiajie.

There are international flight in Huanghua Airport in Changsha which is the capital of Hunan Province where Fenghuang Cheng is. After take off plane, you can take bus to Fenghuang but it is not easy, because the bus driver are not good at English. You may have try to write the name of Fenghuang Cheng on the paper to show taxi travel to the town. They can read the pronunciation.

I'm not sure if this info helps. I'll be covering this region for our company trip next month. And from the itinerary, I see that we can fly from KL to Guangzhou and then via a domestic flight to Dayong. I guess from Dayong you will be able to find transport to Feng Huang easily.