Right now the winds across the Atlantic are blowing over Maine. Generally planes like to go with the wind so they can go faster and be more fuel efficient. Everyday ATC in Scotland decides which routes are best for that particular day. Recently they have been reentering US airspace above Maine so we see more planes along with atmospheric conditions being just right to make the contrails. This plus increased travel around the holidays. If you want to learn more there is a Wikipedia page on North Atlantic Tracks. If you want to see the routes the planes are taking you can go onto a website called flight aware, click on World Hi, this will show you all the “roads” the planes take. Next hit layers and go to the nav page and enable North Atlantic Tracks east and west to see the routes the planes will take. You can also download a flight tracker app and you will see a bunch of planes basically all in a row following these routes.