The Birmingham-based company said in a statement it was working with airport authorities to determine why the sign fell.
"This is a terrible tragedy that none of us fully understand, and we hope that the family who lost their loved one will find strength through prayer and the support of all of us," the statement said.
At St. Thomas More, hundreds of worshippers showed up for a Saturday morning Mass that usually has about 75 people. Luke's uncle Alex Bresette placed a Rockhurst High School jersey on the altar.
"He would have been in the Class of 2020," he told the Kansas City Star.
Ryan Bresette said in a message on Facebook that words cannot describe the pain the family feels.
In a note to his son, he wrote, "I miss and love Luke so very much. I love you Luke!"
"Ryan is especially grateful for the amazing support of the people in Birmingham. They even started a fund for the family at a bank there," Farnan said. "There are long, loving arms that stretch between Birmingham and Kansas City."