How old is too old to be a lap child? It cost this couple $4,000 to find out.

Leslie Hillandahl and her husband received an unpleasant surprise when they tried to check in for their return flight from Italy. Their son, who had recently turned two was now too old to be a lap child. He would need his own seat — at an additional cost of $4,000.

The couple paid the fee and flew home. But Hillandahl wants a refund.