Windows closed and locked, I read the checklist. When we got to the APU start, I reached to the forward overhead panel and hit the start switch. The rest was automatic. With generators online, we set about entering the flight plan to Phoenix into the flight management system, aligning the inertial reference system and getting the cabin comfortable. Tony turned to me and said, "Want to get our clearance?" Fumbling for the mic switch, I announced to Boeing Clearance Delivery, "Boeing Clearance, Southwest five thousand one to Phoenix with Papa," in my best airline captain voice. The response was quick: "Cleared Kent Four Departure, J5 SUMMA, (garbled), direct Kimberly, as filed, maintain two, expect Flight Level 370 10 minutes after departure, squawk 3545."