Czech police were questioning a 34-year-old man who they said made a hoax bomb threat against a Lufthansa flight that landed in Prague on Friday, Reuters quoted a police spokeswoman as saying. Police and bomb experts found no explosive device after searching the plane and 144 passengers for several hours when the Frankfurt to Prague flight landed around 10:40 a.m. Airport operations were not affected, a spokeswoman for Vaclav Havel Airport Prague said earlier. Officers were questioning a man with a mental illness who they believe phoned in the threat, saying what he described as terrorists were on the plane, the police spokeswoman said.