Flight 6013 was destined for Columbus, Ohio, from Las Vegas on Wednesday when a medical emergency broke out mid-flight. One of the pilots urgently required medical attention, leaving only one pilot in a position to fly the plane. But thankfully the off-duty pilot from another airline was on board and ready to step in at a moment's notice. The latest incident follows a string of reports where pilots have been taken ill mid-flight. Aviation watchers have said this was the fifth time in just three weeks. The U.S. Department of Transportation released a safety alert for aircraft operators yesterday, waring...