(Adds detail from aviation official, Mango)
JOHANNESBURG, Oct 23 (Reuters) - South African Airways (SAA) and Comair began returning grounded planes to service a day after South Africa's air safety regulator flagged maintenance problems.
Flights were departing Johannesburg's OR Tambo airport as normal on Wednesday, a passenger service representative for Airports Company South Africa said.
Comair said it expected no disruptions, after at least eight of its domestic flights were hit on Tuesday.
SAA, which had 25 aircraft affected by the safety audit, did not respond to an emailed request for comment.
The South African Civil Aviation Authority (SACAA) said it had found faults during an inspection at SAA Technical. It issued a prohibition order until these had been fixed but did not disclose what they were.
SACAA official Luvuyo Silandela told state broadcaster SABC that the regulator had found that work done by SAA Technical had been signed off by engineers "who do not hold the specific ratings to release that work".
The regulator also had concerns about maintenance checks on components like the flight data recorder and cockpit voice recorders, Silandela said, adding that he wished to dispel allegations that SAA Technical had used bogus parts in planes.
SACAA, which did not respond to emailed requests for comment, said it had accepted a corrective action plan from SAA's maintenance unit and that the decision by SAA and Comair to "self-ground" some aircraft was a precautionary measure.
The lack of clarity over the exact nature of the faults at SAA Technical has led to speculation from analysts that the regulator had found serious infringements.
SAA Technical maintains aircraft for SAA, its subsidiary Mango Airlines and British Airways franchise partner Comair, which also operates under the kulula.com brand.
Mango Airlines flights had left Johannesburg for Cape Town on time on Wednesday, its website showed.
SAA, which has not made an annual profit since 2011 and is dependent on government bailouts, cancelled four domestic flights on Tuesday, combining services and deploying bigger aircraft to accommodate affected passengers. (Reporting by Alexander Winning; editing by Jason Neely and Alexander Smith)