The Civil Aviation Authority of Vietnam (CAAV) said recently that it found many Vietjet pilots had worked above the designated limit of 100 flight hours per 28 days.

Vietjet has explained to the authority that it has faced challenges in its transition to a new scheduling and data tracking software, resulting in poor management of pilots’ flight times, the CAAV said in a report to the Ministry of Transport.

The airline later complied with the CAAV’s regulations and withdrew pilots from further flights if they met or exceeded the CAAV’s flight time threshold.

This has resulted in many Vietjet flights delayed between last Friday and Sunday, the CAAV said.

Over the weekend, a large number of Vietjet passengers expressed anger as their flights were delayed or canceled at airports in Hanoi, Ho Chi Minh City, Hai Phong and Da Nang. Some passengers reported their flights were delayed by seven hours.

Vietjet said Saturday that it had rented more airplanes and crew to cover for the delayed flights, but as this process also faced difficulties, many of its flights could not proceed as scheduled.

Vietjet had the lowest on-time performance last month, according to the CAAV.

Only 82 percent of its flights were on time, compared to 95.2 percent for private airline Bamboo Airways, 89.6 percent for Vietnam Airlines and 85.8 percent of Jetstar Pacific.