Japan Post on Friday resumed accepting Express Mail Service and airmail bound for Ukraine after securing cargo space on aircraft.

The company had been unable to accept such airmail since late February due to prolonged disruptions in distribution networks caused by the COVID-19 pandemic and Russia’s invasion of Ukraine.

The company said there is a possibility of significant delays immediately after the resumption of the services due to the high concentration of shipments.

A Japan Post official said airmail to Ukraine took roughly two weeks to arrive before the pandemic, but the company is not sure how long it will take now.

Mail sent by sea and other services will continue to be suspended, the company said.

The firm also announced on Monday that it will return to senders international mail sent by sea and parcels stuck in transit to six countries, including Russia, starting in late May.

It became difficult to deliver them because of the disruptions in distribution networks caused by the pandemic, and distribution routes had been cut by the Ukraine crisis, it said.

The cost paid by the senders will be refunded.

The items to be returned include letters, postcards, and approximately 20,000 parcels accepted between November last year and January this year. They are currently stored on board container ships and in warehouses overseas. After the letters and parcels arrive in Japan, they will be delivered to the senders’ address.

The decision will apply to deliveries bound for Russia and its neighboring countries — Belarus, Kazakhstan, Kyrgyzstan, Tajikistan and Uzbekistan — to which the sea mail was supposed to be transported via Russia.

Japan Post had stopped accepting international mail by sea destined for the six countries on Jan. 27.