Tensions between Bulgaria and Russia grew when President Rosen Plevneliev described Russia as "a nationalist and aggressive state" for its involvement in Ukraine.
Suggestions from outgoing Defence Minister Shalamanov that Bulgaria might buy used F-16s from Italy or Greece, or Eurofighters from Portugal, prompted Russian Deputy Prime Minister Dmitry Rogozin to tweet: "News from Bulgaria: a certain Shalamanov has convinced Prime Minister Bliznashki to once again betray Russia... in favour of second-hand eagles."
That comment sparked a reaction from Bulgarian Foreign Minister Daniel Mitov who said such comments were "extremely unworthy, contrary to good manners and show
a lack of respect for Bulgarian institutions".
Mr Shalamanov told the BBC that reliance on outdated Soviet-era equipment, which still needs spare parts and maintenance in Russia, was the result of 10-15 years of mismanagement of the Bulgarian armed forces.
As a result, he said, in the current Nato standoff with Russia over its role in the conflict in Ukraine, Bulgaria was having to depend on its neighbours, Greece and Romania, to help police its own Black Sea borders.