Yup. Extensively. The accounts of the interviews are widespread. He got pulled out of a grocery store, as his shift ended just as the skyjacking began.
However, there is uncertainty about whether Dan Cooper signed his ticket, or the agent, Dennis Lysne did. Most feel that Lysne signed the tix, not Coop. But Colbert is leading the charge otherwise...
For more details see SKYJACK, NORJAK, and other books on Cooper.