Balkan Airlines` syndicates demand the sale of four TU 154-M planes be annulled. The complaint, filed in the Sofia Municipal Court, states the sale price is much lower than the actual market value. This is the latest in a series of measures to safe the airline after the failed privatization deal with Gad Zeevi, a controversial Israeli businessman under investigation in his own country. The planes were sold this January to a Cypriot company, Vilkania Ltd., by Zeevi for $2.25 M. At present they are leased by Hemus Air Corp., which makes it a defendant in the case. Hemus` flight schedule will not be interrupted by the suit, Balkan syndicates said, since they have not demanded the suspension of the planes.