Federal investigators are digging into the cause of a Cessna crash Sunday that killed a top aviation safety expert and a former NFL star.

Richard McSpadden, 63, and Russ Francis, 70, died after the Cessna Cardinal they were flying crashed near the runway of the Lake Placid Airport, "striking an earth embankment," according to New York State Police.

McSpadden was the head of the Aircraft Owners and Pilots Association's Air Safety Institute, which focuses on curbing crashes of general aviation airplanes.

"The Cessna 177 Cardinal in which Richard was in the right seat experienced an emergency after takeoff," the association said in a statement. "The airplane attempted to return to the airport but failed to make the runway."

The National Transportation Safety Board is leading the investigation. An initial Federal Aviation Administration incident report says the plane "crashed under unknown circumstances short of the runway."

Francis played for the New England Patriots and San Francisco 49ers for a total of 13 seasons and was a two-time All-Pro. He caught five passes for 60 yards as the 49ers won Super Bowl XIX in January 1985.

"We are deeply saddened by the sudden and tragic loss of former New England Patriots tight end Russ Francis," the organization said on social media. "Our condolences are extended to Francis' family and friends."

Francis retired in 1998 and was in the top 15 for tight ends for receptions, touchdowns and receiving yards in a career.

"Russ was a fan favorite throughout his playing career. He was a dynamic player on the field who had an even bigger personality off it. He knew no boundaries, pushed the limits and lived his life to the fullest," Patriots owner Robert Kraft said in a statement.

McSpadden was well respected in aviation circles and was the former commander of the US Air Force Thunderbirds demonstration team, having "led 100 flight demonstrations flying the lead aircraft," according to his Aircraft Owners and Pilots Association biography.

Lake Placid Airport is about 115 miles north of Albany in northern New York.