Until 2007, U.S. rules required airline pilots to retire at 60, but Congress raised the limit to 65.
Backers of the higher age limit say pilot deaths are rare and that there is no medical basis to reinstate the age-60 rule.
"This is going to bring attention back to the issue," said Shirley Phillips, a former pilot trainer and now an aviation professor at Daniel Webster College, "but it's such a rare event that it wouldn't be justified to go back to the age 60."
Safety experts said any health risks posed by older pilots should be balanced against the advantages of experience in the cockpit, which was displayed in January, when US Airways pilot Chesley Sullenberger safely landed in New York's Hudson River after the jetliner was crippled by bird strikes taking off from LaGuardia Airport.
Sullenberger is 58.
According to Federal Aviation Administration records, Thursday's death was the sixth of a pilot at the controls of a U.S. jetliner since the agency started keeping records in 1994. The previous pilots who died during flight ranged in age from 48 to 57.
Captains over 40 must pass a medical exam including an electrocardiogram every six months to keep flying, while most other pilots need yearly checkups.
"All of these guys are required to go through a first-class physical," said John Hansman, an aeronautics professor at MIT. "I'm not sure the risk of a heart attack changes significantly between 60 and 65."
Before Thursday, the last reported death of a pilot on a U.S. commercial flight occurred in 2007. The pilot of a Continental jet flying from Houston to Puerto Vallarta, Mexico, died after takeoff. The plane made a safe emergency landing in Texas.
The previous five pilots who died in flight - all of whom died when the retirement age was still 60
- were 48, 53, 55, 56 and 57, according to the FAA.
FAA spokesman Roland Herwig said that when considering six deaths, "You need to balance that with hundreds of thousands of flights every year."
The FAA installed the mandatory retirement age in 1960 out of concern that older pilots were more likely to be stricken with a medical problem in flight. Congress and President George W. Bush raised the age in 2007, bringing the U.S. in line with international standards.
On international flights, however, at least one pilot must be under 60.
The issue of just when pilots should be forced from the cockpit has long been hotly debated in pilots' circles, with many younger pilots favoring the age-60 cutoff.
Pilots unions long opposed changing the rule. Ralph Hunter, then the president of the union at American Airlines, told Congress in 2005 that if the retirement age were raised, "we would find out how old is too old
- and I don't think anyone wants to be on that particular flight."
But momentum to raise the retirement age grew after an international aviation body let pilots work until 65. In Congress, backers of the higher age limit said the best, most experienced pilots were being forced to retire too soon.