Seattle-bound United flight 1603, which took off from Houston with 161 passengers on board, landed safely and the pilot was rushed to a local hospital, Boise Airport spokeswoman Patti Miller said.
The pilot, whose name was not released, died as a result of the medical emergency, United spokeswoman Christen David said on Friday.
The Boeing 737 aircraft later continued on to Seattle, landing just after midnight local time, David said.