...ministry said on Thursday.
Some 50 out of 120 controllers went on strike early on Thursday, demanding a smaller workload and more training to maintain flight safety.
They have also called for Roman Biro, the head of the state-run Slovak Air Traffic Services (LPS), to be replaced.
"The talks have hit a deadlock, and the strike continues," ministry spokesman, Marian Janosik, said. "They want us to sack the LPS director, but we see no reason for that."
Only 300 airplanes out of the expected 800 were estimated to have flown over the EU member country on Thursday, news TV station TA3 reported.
Flights to and from Slovakia's main airport in Bratislava were not affected as its controllers did not join the strike.
Air traffic over Slovakia has doubled since 2000 to 340,000 flights last year, putting pressure on controllers, the Slovak Association of Air Traffic Controllers (ATCA) said. Some 1,400 planes a day flew over the country in summer months of 2006.
ATCA said a lack of training hampered safety.
The ministry said it did not consider the safety situation as serious as ATCA described, but added it would address the technical measures demanded by controllers.
[BRATISLAVA/Reuters/Finance.cz]