Narrative:

Climbing to cruise altitude; flight attendant called to report loud noise and vibration below aircraft. [We] declared emergency [and] returned to [departure airport] for inspection. Descent/landing [were] uneventful. Crash crew found 4x4 foot panel hanging below aircraft. Taxied into gate and transferred to another airplane.

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Original NASA ASRS Text

Title: Air carrier Captain reported a large skin panel came loose in flight; causing noise and vibration. They declared an emergency and returned to departure airport.

Narrative: Climbing to cruise altitude; Flight Attendant called to report loud noise and vibration below aircraft. [We] declared emergency [and] returned to [departure airport] for inspection. Descent/landing [were] uneventful. Crash crew found 4x4 foot panel hanging below aircraft. Taxied into gate and transferred to another airplane.

Data retrieved from NASA's ASRS site as of April 2012 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.