Imagine flying over the Colorado Rockies in a single-engine plane when the propeller comes off and you can't see because your windshield is covered with engine oil.That's what happened to an Aspen pilot and his three passengers Wednesday morning after they took off from the Aspen-Pitkin County airport and started climbing to 16,000 feet for a trip to Denver.Barry Cox said he experienced trouble with his 1988 Piper Malibu about 10 minutes after liftoff from the Aspen airport. Engine oil covered the windshield and he turned around to head back to the airport.The next thing he knew, there was a loud "boom" and he lost engine power, even though the engine was running. Cox didn't know the propeller had fallen off because he couldn't see out the front oil-covered windshield.Cox began gliding back to the airport, using the side windows to see where he was going."The hardest part was landing without any visibility. I landed faster and longer than I wanted to," Cox told the Aspen Daily News.Assistant Aviation Director for the airport David Ulane talked to the Aspen Times about the remarkable event."He just did a tremendous job," said Ulane, who witnessed the emergency landing. "Not only did he land without a propeller, he wasnt able to see out the front. Its one of the more tremendous things Ive seen."The plane had to be towed off the runway after he coasted to a stop.Cox, with 30 years flying experience, was taking his daughter and her friend to Denver International Airport. Another friend was going along to get to a doctor's appointment in Denver.What did Cox think of all?"It was exciting," he said.