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MANILA - The Civil Aeronautics Board is investigating Cebu Pacific's cancellation of roughly 50 flights since last week, the agency's spokesperson said Monday.

The "unprecedented" flight disruption was due to various factors, including several damaged aircraft and heavy traffic that prevented flights from taking off and landing on time, the country's largest carrier earlier said.

• LIST: Cebu Pacific cancels dozens of flights on April 28 - 30

• Cebu Pacific cancels several April 24 flights due to 'limitations'

CAB on Sunday started monitoring the routes of the cancelled flights and gathered data on a birdstrike that reportedly damaged one of Cebu Pacific's planes, said agency spokesperson Atty. Wyrlou Samodio.

"Aalamin po natin kasi hindi naman puwedeng basta sabihin lang nila na air traffic dahil unang-una may ibang airlines na nakakalipad -- bakit sila lang ang hindi?" he told radio DZMM.

(We will investigate because they can't just cite air traffic because first of all other airlines are still operating -- why aren't they the only one that can't?)

"Kadalasan po kasi may mga piloto at may mga tao rin from the airlines na ginagamit na dahilan ang air traffic congestion kahit wala naman," he added.

(Usually, there are pilots and airline personnel who cite air traffic congestion even though there is none.)

Cebu Pacific, he said, should notify all passengers of the canceled flights. It was also directed to submit documentary evidence that it provided hotel accommodations to travelers who were already at the airport before the operation disruption was announced, said Samodio.

The airline has apologized for the incident, saying it was extending "every possible help" to passengers.