Dozens of flights were cancelled on Tuesday, after around 500 Helsinki Airport ground staff members walked off the job over losing access to Finnair's standby tickets.
The policy change, which workers said came as a surprise, impacts around 1,000 ground handling staff members not directly employed by Finnair.
"It was a unilateral announcement, and that was it," said Sami Rajala of the Finnish Aviation Union.
The standby ticket benefit for ground staff dates back to 2009, when Finnair first outsourced some of its services, according to Rajala. The perk, known as a Zonal Employee Discount, brings down airfare prices for recipients, provided there is enough room on a flight.
The Finnish Aviation Union was not behind Tuesday's industrial action. The walkout included workers at Aviator Airport Services Finland, Swissport Finland and RTG Ground Handling.
The shop stewards of these companies declined to comment to Yle on the matter on Wednesday. Yle also requested comments from Finnair, but the company had not responded by Wednesday evening.
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