WestJet says it will be issuing flight cancellations “for the foreseeable future” after planes were damaged by a Calgary hailstorm last week, upending travel plans for thousands of passengers. The country’s second-biggest carrier says 16 aircraft, or 10 percent of its fleet, remain out of commission nine days after the tempest rained down golf ball-sized ice pellets onto parts of southern Alberta, including the province’s largest airport.

After assessing the damage, the airline says sourcing specialized equipment and materials to complete repairs and inspections will take several weeks.

WestJet says it has cancelled more than 600 flights since Aug. 5, with 50 trips per day on average now being called off and more than 20,000 customers affected.

The Calgary-based company says fewer flights will be scrapped as planes return to service later this month, but that it shares passengers’ frustration over the impact of the storm.

The airline says it is facing “very high volumes” of calls and emails as it works to help passengers rebook or opt for refunds.

Experts say airfares will likely rise in the short-term due to the diminished flight capacity following the hailstorm, which also damaged the Calgary airport’s domestic terminal and four planes at Flair Airlines and Cargojet.