The invention relates to a method for joining at least two aircraft fuselage segments (2, 3) by friction stir welding with a tool (8) generating friction heat for the partial plasticisation of an edge region (6, 7) of at least one of the two aircraft fuselage segments and a counter bearing (10) for absorbing the force exerted by the tool (8) on at least one of the two aircraft fuselage segments, wherein at least one of the two aircraft fuselage segments comprises at least one rib (17) and/or one stringer (16).In order to minimise the necessary expense incurred in association with the production aids for the FSW process, it is proposed that the at least one rib (17) and/or the at least one stringer (16) of the at least one aircraft fuselage segment (2, 3) should be used as a counter bearing (10).