For his infant son’s first flight, Timothy Ketcham took the extra steps, for both comfort and safety, of buying the 6-month-old his own first-class seat. But when it came time to board an American Airlines flight to Charlotte, the plans got nixed: Baby boy had no seat, forced to fly two hours on his mother’s lap. “I know why,” said Ketcham, his dad in Willow Springs. “So they can put more people on the plane, right?” No refund, no explanationThe Ketchams’ air-hassle adds to a summer of discontent in the skies that are now crowded with post-pandemic leisure fliers. To date, Ketcham has gotten n…