Fredrikstad is served by the Norwegian State Railway [url=http://www.nsb.no/]]on the [[Oslo[/url]]-[wiki=06437de3f9b12c97eb8df74634b35941]Halden[/wiki] line. Also some trains to [wiki=7e268c60ba15269bd8aafe315096ecc2]Gothenburg[/wiki] and onward connections.
There are two main airports serving eastern Norway, the larger one is Oslo Gardermoen (OSL), which unfortunately is far north of [wiki=f4830432874f86d2e2a1a5f2dbebbc80]Oslo[/wiki] while Fredrikstad is far south of Oslo. Nevertheless, there is a bus service ([url=http://www.reiseinfo.no/nbe-www/ruter/r/F11.htm]line F11[/url]) between Fredrikstad and the airport taking slightly over two hours. Ryanair flies to Rygge near [wiki=58091cd419f36b3852b27525492a5d46]Moss[/wiki] (30 minutes from Fredrikstad). Also Norwegian and a selection of charter companies service this airport.
Some people find a good deal if they fly to [wiki=7e268c60ba15269bd8aafe315096ecc2]Gothenburg[/wiki] instead, and take the train or drive from there. Gothenburg is even further from Fredrikstad than OSL is (though the difference in time is less than an hour), but sometimes the tickets might be better there.
Hourly to Oslo via Moss by TimEkspressen.
Several daily to [wiki=322dfd313458cd423c929ffef0b11432]Strømstad[/wiki] in Sweden, corresponding with a ferry to [wiki=04bd74d9bb02221cb5593c4a97371fb1]Sandefjord[/wiki].