Cebu Pacific. Instagram.com/cebupacificair

MANILA -- An expanding network and flight crew transferring to higher-paying airlines have put a strain on Cebu Pacific's manpower, airline personnel said Wednesday, as the carrier pushed through an unprecedented wave of cancellations.

Some 22,000 passengers of the Philippines' largest airline were affected by over 100 cancellations until the middle of May, which it blamed on "intertwined" factors such as heavy traffic and damaged aircraft.

Under Philippine aviation law, cabin crew can work for a maximum of 14 hours, to be followed by at least 12 hours of rest. They also can't fly for 7 consecutive days.

"Kulang kasi 'yung manpower. Nagdadagdag sila ng flights, tapos hindi na-anticipate ang dami ng nagresign at nagmaternity leave," a senior airline personnel told ABS-CBN News, requesting anonymity for lack of authority to speak to the media.

(The manpower is lacking. They added flights without anticipating the number of those who will resign or take maternity leaves.)

"I could say na overworked talaga ang mga FA's at pilots sa amin kaya dami din umaalis," the source said.

(I could say that flight attendants and pilots are overworked, that's why many left.)

Some pilots left Cebu Pacific to work for international carriers that pay double or triple, an airline staff involved in flight operations told ABS-CBN News in a separate interview.

"Dito kasi, typical Filipino company na susulitin yung bayad sayo. Basta may 8 hours rest na sila, bibigyan na sila lipad," the staff said.

(It's a typical Filipino company that will squeeze as much out of you. As soon as they're rested for 8 hours, they're asked to fly again.)

"'Yung iba pagod pa, ayaw lumipad pero sa regulation kasi 8 o 12 hours na rest lang required," the staff added.

(Some are tired. They don't want to fly but regulations only require 8 to 12 hours of rest.)

Cebu Pacific spokesperson Charo Logarta Lagamon earlier Wednesday denied reports that the flight cancellations were due to absent staff.

The absence of some employees is "only natural" and has been "factored in" operations of the Philippines' largest airline, Lagamon said.

Some crew members have been working even on their days off because "they want to render duty, they want to help the passengers," Lagamon told DZMM.

The senior airline employee said the Gokongwei-led airline has addressed some concerns, with FAs no longer required to clean lavatories or collect garbage.

The employee is sticking it out with Cebu Pacific, citing its "happy" work environment and young workforce.