Salah Al Shaikhly, the new Iraqi ambassador in London, said Jaafari arrived in London, where he lived as an exile during Saddam's rule, for a private visit during which he will meet members of the Iraqi community.
Government spokesman Laith Kubba said from Baghdad that Jaafari had flown from Kuwait, the airline's "longest flight since 1990 owing to the limited capabilities of Iraqi aircraft". Jaafari flew on a Boeing 727, one of two planes owned by the Iraqi flag carrier, with the other being a slightly more recent Boeing 737.
Iraqi Airways operates daily flights from Baghdad to Amman, and flies three times a week to the Iraqi cities of Arbil and Basra, and to Damascus. International flights resumed last September.
The UN sanctions were lifted after the US-led invasion that toppled Saddam in April 2003.
Jaafari will leave London on the same plane to travel to Brussels for an international conference on rebuilding Iraq sponsored by the European Union and US that will be held Wednesday, the ambassador said.
He will then travel to Washington before returning to London, where he will have talks with British officials, the ambassador added.