According to the report, the boy went missing for two hours after disembarking the plane on his own.
Poosaala also claimed that no one contacted the boy's uncle, who was waiting at the airport, to tell him the boy had arrived. Instead, he was contacted by phone by a man who said the boy was with him and then hung up.
The boy eventually emerged from the airport gate with an unidentified man who left when he saw the uncle.
Poosaala later wrote to Cathay and complained that his son could have been kidnapped or used to smuggle illegal items.
He was originally offered US$75 ($106) in compensation, which was later increased to US$200 ($283).
However, the father decided to sue the airline in order to prevent similar incidents from happening in the future.
According to Cathay's website, the service for an unaccompanied minor starts at US$64.
"Cathay Pacific will care for your child throughout the journey until the child passenger is collected by the nominated adult at the arriving airport. The responsible person meeting the child at the arrival airport must provide proof of identification before your child is handed over," the website reads.
It also states that the airline does not accept Unaccompanied Minors with an itinerary that includes a transfer exceeding five hours.
While there are no direct flights between Hong Kong and Hyderabad, it was unclear whether this was why Raja Ram Poosaala was allegedly left unattended.
A spokesperson for the airline told MailOnline Travel they were unable to comment while legal proceedings were underway.
