NRC attributed the growth of the passengers to the closure of Nnamdi Azikiwe International Airport, Abuja for repair works.
Mr Victor Aduma, the rail service operations manager, made this known to the News Agency of Nigeria (NAN) on Wednesday in Abuja.
According to him, a total of 2,822 passengers joined the service on a free-ride to the Kaduna Airport while 15,972 passengers went on normal trip since March.8.
"We started Kaduna Airport free service on March 8; the volume of passengers have been high.
"The aim is to ease the pain on passengers connecting their flight at Kaduna pending when the repair works at the Nnamdi Azikiwe International Airport, Abuja is over," he said.
Adamu said that the ride had been hitch-free except for the urgent need of more coaches.
According to him, the volume of passengers had outgrown the four coaches on ground.