Processes for producing jet fuel are disclosed. In one embodiment, syngas is converted to methanol, and a first portion of the methanol is converted to olefins using a methanol-to-olefins catalyst. The olefins are then oligomerized under conditions that provide olefins in the jet fuel range. The olefins can then optionally be isomerized and/or hydrotreated. A second portion of the methanol is converted to dimethyl ether, which is then reacted over a catalyst to form jet fuel-range hydrocarbons and aromatics. All or part of the two separate product streams can be combined, to provide jet fuel components which include isoparaffins and aromatics in the jet fuel range. The syngas is preferably derived from biomass or another renewable carbon-containing feedstock, thereby providing a biorefining process for the production of renewable jet fuel. In another embodiment, the process starts with methanol, rather than producing the methanol from syngas.