Frontier Airlines has canceled more than 50 flights through Saturday because of a Wednesday night hailstorm in Denver that knocked nearly a third of its large planes out of service. The airline said 18 of its 59 Airbus planes and two turbo-props were damaged in the storm that hit Denver International Airport. Five planes could be returned to service this weekend, but others are being moved to maintenance bases around the country for repairs that could take longer.The planes have damaged from dents to tears caused by ping pong sized hail, said a Frontier spokesman. The airline said it will take three to five days to repair a majority of the planes. Frontier is urging travelers to check their flight status online -- not to call the airline -- and is waiving change fees for those who need to reschedule their flights. The airline also said it's booking passengers on other airlines with available seats. But it's urging travelers who don't need to travel to, from or through Denver on Friday or Saturday to delay their trips.Frontier passengers saw long lines on Thursday as they tried to find a flight out."No luggage, no anything. I'm in the same clothes for awhile and pretty tired," said one frustrated passenger. "They canceled two flights yesterday. Hoping to get out today. Going to Montana but now I'm going through Seattle."A spokesman for United Airlines, the largest carrier in Denver, didn't immediately return a call.