responsive two-column layout

This might be a really basic question, but I am trying to figure out how to best create a responsive two-column layout. Let's say you have two sets of data. For example, latest departures and arrivals at the airport. One is not really more important than the other, so it's hard to prioritize one over the other. On a normal large screen, I have them side by side, so you can look left or right depending on the info you need. However, I am not sure what is the best place to manage this on smaller mobile screens.

All the responsive multi-column layouts seem to treat the page like a newspaper where each column is a continuation of the previous. When the screen is smaller, the columns end up stacked on top of each other. Is there a good example of how to treat two columns as equals?