Tracking airfare as a proxy for summer travel plans

<img width=“750” height=“393” src=“https://i0.wp.com/flowingdata.com/wp-content/uploads/2021/04/airfare-difference.png?fit=750%2C393&ssl=1" class=“attachment-medium size-medium wp-post-image” alt=“” loading=“lazy” srcset=“https://i0.wp.com/flowingdata.com/wp-content/uploads/2021/04/airfare-difference.png?w=1572&ssl=1 1572w, https://i0.wp.com/flowingdata.com/wp-content/uploads/2021/04/airfare-difference.png?resize=750%2C393&ssl=1 750w, https://i0.wp.com/flowingdata.com/wp-content/upl …