A Qantas flight from Melbourne to Darwin was disrupted when passengers refused to buckle their seatbelts in protest at the attempted deportation of a Tamil asylum seeker by immigration authorities.

Qantas confirmed a "number of passengers" on QF838 became disruptive when they refused to sit down and follow cabin crew instructions on the Monday morning flight.

Qantas reported an underlying pretax profit of $367 million in the first half, up from a $252 million loss the previous year. Credit:Getty Images

The 25-year-old Tamil man, Puvaneethan, who was on the plane, was being deported to Sri Lanka after the Refugee Review Tribunal found him not to be a refugee. He has been living in Australia since 2012.

"After boarding QF838 in Melbourne, a number of passengers became disruptive. The passengers refused to follow cabin crew instruction so were offloaded and met by the AFP," a Qantas spokeswoman said.