For those who are interested in the details, the Finnish Air Force sent 5 Hornets up in the morning of the 15th for "one dogfight training sortie" at altitudes of 18000 ft and below. Duration is not given but the mission covered several hundred square km. On return to base, clearly visible layers of flour-like dust was discovered around the air intakes of three of the five a/c, after which it was decided to perform a thorough examination to determine the extent of damage if any.
A pdf file of slides used in yesterday´s press conference here (language only in Finnish):
http://www.ilmavoimat.fi/filebank/5377-tuhkatilanne.pdf
The latest is, engine components with particle concentrations will be replaced and said components will undergo further tests.