Off-duty pilot saves the day on Southwest flight after captain falls ill.

A Southwest Airlines flight bound for Columbus had to turn back to Las Vegas after its captain became "incapacitated" and required medical attention. A pilot from another airline, who was on board the plane, entered the flight deck and assisted with radio communication as a Southwest pilot flew the aircraft. The flight was able to land safely and an alternate crew took over. The condition of the pilot who required medical attention was not immediately clear.