Slowly but surely, airports are working out ways to include ride-hailing service such as Uber and Wingz and Lyft into their ground transportation offering.

Seattle-Tacoma International Airport is the latest to join in, but their program has an environmental twist.

Back in 2003, the airport was the first in the country to mandate and achieve a 100 percent green taxi fleet.

Now, in a one-year pilot program that kicks off today, any ride-hailing service that wants to operate at the airport will be required to match those green fleet requirements through a combination of high MPG vehicles, deadhead reduction, and/or ridesharing, the airport said in a release.

Services that want to participate in the program will need to sign agreements with the Port of Seattle, prove their compliance and pay a $5 fee for each pick-up at the airport.

According to the Seattle Times , both Uber and Lyft have already signed the agreements and will begin service today, with Wingz planning to roll out service next week.

The ride-hailing companies will be required to file monthly reports on all pick-ups and drop offs and pay an additional $5 per trip fee if they don’t meet the environmental standards.

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