About a hundred Greek flights will be grounded on Thursday due to a 24-hour strike by Olympic Airlines unions opposing the government's plan to privatize the ailing flag carrier, the company said on Wednesday.

Greece's conservative government last month launched a tender to sell-off debt-ridden Olympic. It has said Qatar Airways is among the investors interested in the sale, which unions strongly oppose despite compensation promises.

"Olympic Airlines has decided to suspend 46 return flights, both domestic and international, due to its unions' strike on October 30," company spokesman Michalis Mygiakis said.

Flights between Athens and Milan, Rome, Frankfurt, Brussels, Belgrade and London are among those affected.

Airport officials and unions said hundreds of Olympic Air workers walked off their job on Wednesday and marched on the Athens airport taxi ways protesting the sell-off plan but without causing flight disruptions or serious delays.

Air traffic controllers said the protesters had scrawled graffiti on a small aircraft owned by Pantheon, the holding company set up to manage Olympic's airline assets during the privatization.

"I am now walking on the runway with my colleagues," Kleanthis Tratras, an Olympic airlines technician said. "We won't allow the sale of Olympic. We will be here tomorrow; we will be here until our voices are heard."