The head of the air traffic controllers' local in Allentown told the Allentown (Pa.) Morning Call Tuesday that the control tower at Lehigh Valley International Airport did not have enough experienced personnel on duty when the incident occurred Friday night.
The National Transportation Safety Board said United Express Flight 7138 bound for Chicago had to swerve to avoid hitting a single engine Cessna as it raced down the runway with 39 passengers aboard.
Union Chapter President Jeff Fisher said the two controllers on duty at the time were both certified controllers, but were also considered to be trainees.
"The more trainees you have in the building, the more likely it is that a mistake is going to happen," said Fisher.
The NTSB said Monday it was investigating all aspects of the incident, including air traffic control.