The transport ministry on Monday approved Skymark Airlines Co.'s application to begin flights between Tokyo and Sapporo despite recent safety problems at the airline.

The Tokyo-based carrier plans to begin flights on April 28, with 10 round trips daily between Tokyo's Haneda airport and New Chitose Airport near Sapporo.

The route is one of the world's busiest.

At the same time, however, the Land, Infrastructure and Transport Ministry instructed Skymark to improve its safety management system and submit specific improvement measures by April 24.

The transport ministry said it will reconsider its approval of the route if the startup carrier fails to submit the safety plan.

"We are sorry for causing trouble. We will review our operations and take necessary measures," Skymark President Shinichi Nishikubo said when he was handed the order by Teiji Iwasaki, chief of the transport ministry's Civil Aviation Bureau.

Skymark was found to have operated an aircraft some nine months beyond its scheduled maintenance date, prompting the ministry to intensify scrutiny of the carrier since March 17.

The ministry's investigation revealed a lack of maintenance verification, citing cases in which safety information was not passed along to the appropriate people.

Skymark has also suffered from frequent changes in maintenance personnel, whose backgrounds vary. The lack of uniform maintenance procedures also contributed to confusion, the ministry said.