The US Airways jet that survived a crash-landing in the Hudson River lay in a thickening flow of ice Saturday as the bitter cold complicated efforts to retrieve a jet that now appears to be more intact than previously thought. Federal investigators said the aircraft's right engine, which they initially believed had come off and drifted away, is still attached to the plane. Investigators encountered treacherous conditions Saturday as they contemplated how to best hoist the jet from the water without damaging it. Big patches of ice had formed around the plane Saturday morning as the temperature fell to 6 degrees (minus 14 Celsius). National Safety Transportation Board member Kitty Higgins said the agency and salvage company officials were still trying to work out the logistics of how to lift the 80-ton plane onto a barge. The partially submerged plane is tethered to a sea wall in lower Manhattan. Crews will use a crane to raise the plane a few feet (meters) at a time to let the water drain out, possibly with the help of bilge pumps. Load cells will be attached to each wing to measure the plane's weight as it comes out of the water. Once out of the water it will be examined by investigators. Divers and sonar operators hunted for the missing engine in the cold, dark and murky river. The engine was lost when the plane hit the water after a bird strike. Exactly where the engine is though, is a mystery. Authorities want to inspect the engines to figure out how exactly the birds caused the plane to fail. One clue could be the feathers of the birds to identify which species was involved. identifying which kind of birds cold help prevent future mishaps. A National Transportation Safety Board spokesman said the water was so murky - even before ice began to form - that authorities couldn't see the engine still on the plane. Investigators began interviewing the pilot, Chesley B. “Sully” Sullenberger, and his co-pilot for the first time Saturday, said NTSB spokeswoman Bridget Serchak.