Narrative:

We were to reposition for repairs and a flight attendant wanting to go home. He could not get on the flight that was leaving at the time due to an unknown reason. He wanted to come with us on the reposition flight. The captain approved and got dispatch to add him to the release. When we were on the airplane maintenance came back with the log and told us that it is to be a ferry flight due to the left engine being 'marginal.' the captain later got the signed ferry permit and we left. I did not look at the permit and I trusted that the paperwork was in order because I have never done a ferry flight before. Come to find out later that the ferry permit needed to have the flight attendant's name on it as well. Also; after takeoff; we got a smoke toilet caution message on the EICAS display and asked the flight attendant who was in the first row to go back and investigate. The flight attendant came up to the cockpit and told us that there was smoke in the cabin. We both looked back and observed the smoke. We then told ATC that we had to return to ZZZ to land due to smoke in the cabin. We were at about 11000 ft MSL and no more than 20 mi from ZZZ. The captain had the flight controls and handled the radios while I performed the actions in the pom emergency actions for the smoke toilet message. I was also running checklists and setting up for a visual approach back in. We landed without incident but only then did we find out that the flight attendant's name had to be on the ferry permit.

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Original NASA ASRS Text

Title: ACR FLT CREW ON FERRY FLIGHT EXPERIENCES LAV SMOKE WARNING SHORTLY AFTER TKOF AND RETURNS TO DEPARTURE ARPT.

Narrative: WE WERE TO REPOSITION FOR REPAIRS AND A FLT ATTENDANT WANTING TO GO HOME. HE COULD NOT GET ON THE FLT THAT WAS LEAVING AT THE TIME DUE TO AN UNKNOWN REASON. HE WANTED TO COME WITH US ON THE REPOSITION FLT. THE CAPT APPROVED AND GOT DISPATCH TO ADD HIM TO THE RELEASE. WHEN WE WERE ON THE AIRPLANE MAINT CAME BACK WITH THE LOG AND TOLD US THAT IT IS TO BE A FERRY FLT DUE TO THE L ENG BEING 'MARGINAL.' THE CAPT LATER GOT THE SIGNED FERRY PERMIT AND WE LEFT. I DID NOT LOOK AT THE PERMIT AND I TRUSTED THAT THE PAPERWORK WAS IN ORDER BECAUSE I HAVE NEVER DONE A FERRY FLT BEFORE. COME TO FIND OUT LATER THAT THE FERRY PERMIT NEEDED TO HAVE THE FLT ATTENDANT'S NAME ON IT AS WELL. ALSO; AFTER TKOF; WE GOT A SMOKE TOILET CAUTION MESSAGE ON THE EICAS DISPLAY AND ASKED THE FLT ATTENDANT WHO WAS IN THE FIRST ROW TO GO BACK AND INVESTIGATE. THE FLT ATTENDANT CAME UP TO THE COCKPIT AND TOLD US THAT THERE WAS SMOKE IN THE CABIN. WE BOTH LOOKED BACK AND OBSERVED THE SMOKE. WE THEN TOLD ATC THAT WE HAD TO RETURN TO ZZZ TO LAND DUE TO SMOKE IN THE CABIN. WE WERE AT ABOUT 11000 FT MSL AND NO MORE THAN 20 MI FROM ZZZ. THE CAPT HAD THE FLT CTLS AND HANDLED THE RADIOS WHILE I PERFORMED THE ACTIONS IN THE POM EMER ACTIONS FOR THE SMOKE TOILET MESSAGE. I WAS ALSO RUNNING CHKLISTS AND SETTING UP FOR A VISUAL APCH BACK IN. WE LANDED WITHOUT INCIDENT BUT ONLY THEN DID WE FIND OUT THAT THE FLT ATTENDANT'S NAME HAD TO BE ON THE FERRY PERMIT.

Data retrieved from NASA's ASRS site as of May 2009 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.