When last I checked, our spy planes used a fuel additive - chlorofluorosufonic acid - to suppress the tell-tale contrails.
This injects chlorine and fluorine, both known ozone destroyers, directly into the upper atmosphere.
OTHO, we peons are not allowed to use freons to keep chlorine and fluorine from damaging the ozone layer...
The aircraft has a bay outboard of each of the main landing gear that was originally supposed to store contrail-suppression chemicals but was never used. The two bays are about 2.75 meters (9 feet) long and are as deep as the wing. The original B-2 design included tanks outboard of the main landing gear that would store a chemical to mix with the exhaust and suppress contrail formation. According to one report, “chlorofluorosulphonic acid” was to be injected into the jet exhaust to eliminate contrails. But this scheme wasn’t actually used. Several other acids were tested too, but the result was that the chemicals were too corrosive.
It seems that “chlorofluorosulphonic acid” is unobtainium, as the term only occurs in a few articles about stealth. Possibly what is meant is “chloro fluoro sulfone” which goes by the IUPAC name “Sulfuryl chloride fluoride” [ClF O2 S]. This compound is employed as a solvent for highly oxidizing compounds, and reacts violently with water.
Sulfonic acid has a sulfur atom bonded to a carbon atom of a hydrocarbon and bonded also to three oxygen atoms, one of which has been attached to a hydrogen atom. Sulfonic acid is acidic due to the hydrogen atom, stronger than a carboxylic acid.
http://www.globalsecurity.org/military/world/stealth-aircraft-vulnerabilities-contrails.htm