Aircraft engineers at Serbian carrier JAT Airways joined a strike by mechanics over pay on Monday, adding a new demand that the company's management be sacked.

"We demand that the (new) general manager sack the entire first and second line of management," union leader Igor Sarenac said.

The mechanics, who carry out manual work on the planes, said earlier in the day they would not halt the strike, now in its fifth day, because no one from management or government had approached them to discuss the issue.

Since Saturday JAT has flown to a few European destinations with hired planes and crews, while its own fleet has been grounded.

The striking mechanics and the more senior engineers are also seeking more detail on planned spin-offs of JAT's non-core businesses, which include technical maintenance services. Aircraft engineers said they wanted that unit to have a long-term contract with JAT.

JAT wants to keep the unit as its subsidiary and later look for a foreign partner for it. General Manager Nebojsa Starcevic said last week the unit would most likely get a three-to-five year exclusive contract with JAT.

The government plans to discuss the situation on Thursday.

JAT plans to keep about 1,500 workers in its core business out of 3,700 now employed.