Luxury jet makers battle over lucrative spy plane niche

Last month, a ghostly grey business jet took off from central Sweden and headed across the Baltic on a routine spying mission.

The converted Gulfstream, caught on a tracking website, was flown by the Swedish Air Force and patrolled an area thick with Russian radar signals off the militarised coast of Kaliningrad.

Apart from a couple of unobtrusive bulges underneath, Sweden's two Gulfstream-based S102B Korpen spy planes look like any other sleek corporate jet.

But inside, the Swedish jets and a growing fleet of newer corporate aircraft contain the eyes and ears of a relentless intelligence war.