News that American Airlines has decided to vacate the US Airways headquarters tower in Tempe came as no surprise. Back in 2013 when they merged, local airline execs vowed to never lose their commitment to being strong corporate citizens in the Valley, even as they were packing up for Texas. Vows in the heat of the moment are one thing. And the airline remains active around town today. But as the years go by, business conditions change, and that trumps vows. You have to wonder what their involvement will look like as time marches on and memories fade.