A California family not allowed to board a cross-country flight said Tuesday that they believe they were discriminated against because their son has Down syndrome.

Robert Vanderhorst, his wife Joan and 16-year-old son Bede, who is disabled, were booked to fly on an American Airlines flight from Newark to Los Angeles on Sunday when the boy and his parents were not allowed on the plane.

The family from Porterville had upgraded to first class tickets at an airport kiosk, and asked the airline to seat the boy and one of his parents together, Vanderhorst said - a request the airline granted.

When the family was ready to board, they were stopped by airline personnel, told their son was a "security risk" and would not be allowed on the flight. The parents protested, and later were rebooked to fly coach with another airline.

American Airlines spokesman Matt Miller said the disabled boy was agitated and running around the gate area prior to boarding, which his parents dispute. The airplane's pilot observed the boy, Miller said, and made the call based on his behavior.

"He was not ready to fly, that was our perspective," Miller said. "We rebooked the family out of concern for the young man's safety and that of other passengers as well."

But Vanderhorst said his son did not run at any time, did not make any loud noises and didn't display any other offensive behaviors. The boy walked around with him or sat quietly in the gate area, Vanderhorst said.

A cell phone video captured by the boy's mother shows Bede sitting and quietly playing with a baseball cap.

Vanderhorst said Bede, a freshman at Granite Hills High School in Porterville, about 70 miles from Fresno, is very charming in contact with other people. The family has flown more than two dozen times with him, without any difficulties.

"Usually my son gets his snack and falls asleep, just like most people," Vanderhorst said. "The problem is this pilot thought my son might not be like most people. He didn't want a disabled person disturbing other passengers in first class."

The family says the pilot might have also been affected by the disabled boy's size - Bede is 5'1 and weighs 160 lbs.

On the second airplane, the family was placed in the last row and no passengers were allowed to sit within two rows of them, Vanderhorst said.

He hoped that airlines would change their mentality when dealing with the disabled.

"It's ridiculous and groundless to claim that this kid created a security risk," he said. "It was the pilot's insecurity. I paid for those seats and there was nothing that should have prevented us from taking that flight."

American Airlines' Miller said the company will reimburse the family for the upgrade fees.