I was on a flight earlier this year when something like this happened. I want to say we were flying into SBP, but I could be wrong. Wherever it was - it was a CRJ that had no channel 9. We had come through the clouds and were descending at a good clip when suddenly the pilot pulled up very sharply. Many gasp and cries throughout the plane. I was face-against-the-window trying to figure out what happened. We circles for 10-15 minutes before the pilot got on the radio and apologized for the sharp maneuver - apparently the fog had rolled in and completely blocked all visability. In the meantime, the lady next to me had a death grip on my arm and was hyperventilating. Several other passengers were crying. I'll admit that my heart was racing and I kept thinking, "Thank god my flight fearing boyfriend isn't with me." The pilot waited ages to announce what was going on - I think he should have done it far sooner. It would have saved a lot of people from freaking out.