G Warwick, Exhaust additives may reduce contrails, Aviation Week & Space Technology, 12-25 January 2026, p 55

In US, the University of Albany in New York  is proposing the introduction of either silver iodide or  bismuth triiodide into jet exhaust to trigger ice crystals of sufficient size to be drawn-out of the atmosphere by gravity.   Simulations show a resulting reduction in cirrus climate effects.