The Tokyo metropolitan government's consumer affairs center said Wednesday that it has sent an official letter of complaint to the operators of Skymark, a low-cost airline headquartered at Tokyo's Haneda Airport, after many passengers mistakenly came to the center to make complaints that should have been directed at the company itself.

The letter of reprimand comes after news that the transport ministry will require Skymark pilots and cabin attendants to undergo onboard observation to ensure they are properly trained, TBS reported.

Skymark has been the subject of a series of security scares and complaints this year. In February, a flight arriving at Miyako Airport in Okinawa made its approach below the legal minimum altitude. In April, a flight landed at Ibaraki Airport without permission. By early May, Skymark had reportedly been involved in six safety violations, a transport ministry official was quoted as saying, TBS reported.