I just bought a 2014 Fiesta less than 48 hours ago. Today when driving with my friend on the highway at about 50 mph the car started to make a wind helicopter sound and you could actually feel the air pressure and vibration inside the car for several miles. We had the air conditioning on. The noise/vibration was worse when the front windows were up. It was intense enough that it scared us and we pulled off the highway and inspected the tires, nothing looked amiss. We rolled the windows down for the ride back to the Ford dealer and took the salesman for a drive and of course the car did not do it again. Any ideas on this? I am thinking I should return the car as I have to believe it will happen again. I am not sure if it is the aerodynamics, seals, or the wheels.