The plane returned to Las Vegas and landed "without incident". "A credentialed Pilot from another airline, who was on board, entered the Flight Deck and assisted with radio communication while our Southwest Pilot flew the aircraft," Southwest Airlines spokesperson Chris Perry said, as per CNN. We greatly appreciated the support and assistance," Mr Perry said. " The condition of the pilot who required medical attention has not been made clear. The FAA stated that it will be investigating the incident. Source -https://www.ndtv.com/world-news/in-us-off-duty-pilot-from-another-airline-helps-land-plane-after-captain-falls-ill-mid-flight-3891581#pfrom=home-ndtv_lateststories