Compression socks! Consider wearing them on your flights. They’ll help increase circulation and lessen swelling. They have the added benefit of helping to decrease risk of DVT as well. On the way back, they’ll also help recovery for your legs after your 10k. You can buy basic ones at drug stores, or Target and Walmart, or buy cute ones! (REI, Duluth Trading Co. Sockwell makes nice ones. You can buy them on Amazon.)