Kourtney Kardashian & Travis Barker Fly Commercial Amid Carbon Footprint Concerns

Intentional or not, Kourtney Kardashian's one-upping her kid sister by traveling like the masses and doing better by the environment ... just as a bunch of celebs -- including her kin -- catch heat for huge carbon footprints.

Kourt and her husband, Travis Barker, flew commercial on Alaska Airlines for a trip from LAX to Spokane, Washington earlier this week. We're told Penelope and North were also on board.

They appeared to keep the whole thing lowkey, putting on their masks and hoodies. We know they have a home in Coeur d'Alene, Idaho, and Spokane is the nearest airport. So, it's likely they'll be spending some time there.

Of course, commercial cruisin' isn't exactly her family's M.O. lately. Remember, a recent report by Yard, a marketing agency, called out celebs polluting the air by taking private jets.

Kim Kardashian and Travis Scott were among the celebs to make that list -- and, as we reported, Kylie Jenner's carbon footprint has also been a hot topic after she posted a shot of her and Travis with his and her private jets.

She also got flak for reportedly using her PJ to go shopping less than 30 miles from home ... just to dodge L.A. traffic.