(CNN) — The 161 passengers aboard United Flight 1603 must have known something was wrong when a crew member announced through the cabin loudspeaker if anyone aboard was a physician.
Capt. Henry Skillern, 63, was suffering a heart attack.
The in-flight emergency Thursday night that began somewhere in the skies between Houston and Seattle prompted the 737 to divert to Boise, Idaho. Air traffic controllers radioed the plane's first officer who updated them with the captain's condition.
"We got a man down, chest compressions going on right now," the first officer said. "I'm not sure too much right now on status."
Once it was on the ground, first responders boarded the airliner and rushed Skillern to Boise's Saint Alphonsus hospital, where he later died.
The tragedy threatens to reignite the debate over FAA age restrictions for commercial airline pilots. In 2007, the mandatory pilot retirement age was raised from 60 to 65. At that time the FAA said five pilots their ages ranging from 48 to 57 had died in-flight since 1994 when the FAA began following that statistic.
When that the FAA was considering changing the rule, then-administrator Marion Blakey underscored the value of pilot experience, calling it "an added margin of safety."
"Foreign airlines have demonstrated that experienced pilots in good health can fly beyond age 60 without compromising safety," she said.
FAA regulations call for a medical examination every year for commercial airline pilots under age 40 and every six months for those over age 40. To pass the exam, they must not have an established medical history or diagnosis of coronary heart disease that has required treatment.
All airline pilots are required to get EKG heart checks at the age of 35. For those age 40 and older, annual EKGs are required.
And airline pilots are required to report any heart disease to the FAA, regardless of when they learn about it.
It wasn't immediately known whether Capt. Skillern was piloting the plane at the time he became incapacitated. Typically, there are two pilots in the cockpit so that during an emergency, either pilot can quickly take control of the aircraft.
Flight 1603's passengers waited at the Boise airport until United flew in another pilot from San Francisco, before they were able to continue their journey to Seattle.