A NATO source confirms that the comment was made by a US diplomatic official, but says the organisation does not know which operating nation, or nations, may have been involved.
F-16s from several nations were in northern Europe late last week to participate in two large-scale exercises.
© German air force
These included Turkish air force examples (above) which arrived at Laage air base in Germany for the “Brilliant Ardent” manoeuvres, and Dutch, Norwegian and Polish fighters which were to participate in the “Frisian Flag” exercise at Leeurwarden in the Netherlands.
Finland's air force late last week released images of the effects of dust contamination on the engines of a Boeing F-18 which had been involved in an exercise in the north of the country on 15 April.