The Bulgarian Ministry of Defence and MIG have signed an agreement for the maintenance of the air force’s MiG-29 fighter jets at Krumovo Air Field, Bulgaria.

MIG deputy CEO Iliya Tarasenko said the agreement involves the modernisation and services of the jetfighters over the next four years.

Bulgarian Deputy Defence Minister Valentin Radev said the Bulgarian Air Force would require an additional 7m-8m lev ($5m-$6m) a year for maintenance of the jetfighters.

The agreement is an extension of the deal to overhaul Bulgarian combat jets by 2020 to protect the country’s air space, according to the Sofia News Agency.

Work under the agreement will be performed by state-owned Terem at the Plovdiv military plant Georgi Benkovski, Bulgaria.