 Firefly consists of a two @-@ hour pilot and thirteen one @-@ hour episodes ( with commercials ) . The series originally premiered in the United States on Fox in September 2002 . The episodes were aired out of the intended order . Although Whedon had designed the show to run for seven years , low ratings resulted in cancellation by Fox in December 2002 after only 11 of the 14 completed episodes had aired in the United States . The three episodes unaired by Fox eventually debuted in 2003 on the Sci Fi Channel in the United Kingdom . Prior to cancellation , some fans , worried about low ratings , formed the Firefly Immediate Assistance campaign whose goal was to support the production of the show by sending in postcards to Fox . After it was canceled , the campaign worked on getting another network such as UPN to pick up the series . The campaign was unsuccessful in securing the show 's continuation . 
