Concern over certification processes led to the blanket ban on Eritrean operators during the latest revision of the European Commission's airline blacklist.
Eritrea's civil aviation authority, ER-CAA, had told the Commission that it had yet to resolve a safety concern over the certification process leading to the issuance of an air operator's certificate.
This had been one of three significant problems - alongside airworthiness and air navigation - originally highlighted during an ICAO audit in November 2010.
The ER-CAA did not submit any information regarding corrective actions to address the certification issue, nor any information on operational oversight of Eritrean carriers, says formal documentation accompanying the Commission's blacklist revision.
Having "declined to attend" previous consultation meetings to clarify the situation, it adds, the ER-CAA gave a presentation to the European air safety committee on 21 November.
While the ER-CAA told the committee it considered the certification issue addressed, this did not convince the committee's representatives.
"In view of the air safety committee they failed to adequately demonstrate they had taken comprehensive action to address all aspects of the significant safety concern," the documentation states.
"They were also unable to provide clarity on the oversight arrangements associated with the aircraft listed on AOCs issued by Eritrea which include wet-leased aircraft from foreign air carriers."
It says that, as a consequence, these aircraft are listed on several AOCs, which "does not comply" with international safety standards.
Eritrean Airlines told the committee it operates two Airbus A320s on services to Rome under a wet-lease arrangement. But the carrier did not satisfy the committee's demand for clarity on oversight and control of its operations.
While the Commission acknowledges the efforts to address Eritrea's safety deficiencies, it says the Eritrean authorities are not yet able to enforce safety standards on the country's airlines.