The Cessna 414 twin-engine aircraft took off from Indianapolis and crashed just short of the Central Illinois Regional Airport in Bloomington after midnight, the Federal Aviation Administration said.
The Chicago Tribune quoted Scott Barrows as saying his daughter's husband, Scott Bittner, 42, was also among several other men on board.
"(They) went to the NCAA game last night and they were flying back and I guess the weather was bad in central Illinois. It was foggy," Barrows told the Tribune. "They were supposed to land around midnight. My daughter was called at 4 a.m. ... It has been confirmed they are dead."
The National Transportation Safety Board was investigating, but there was no initial word on the cause of the crash. News photos from near the scene showed dense fog.
The airport was open and all systems, including its runway lighting, were functioning, though the tower had closed several hours earlier and handed responsibility to an air traffic control facility in Peoria.
"That is not an anomaly; that's a very common thing at airports across the country," airport Director Carl Olson told reporters at the news conference.
Radar contact was lost moments before the crash and a search was launched when the pilot failed to close out his flight plan. It took about three hours to find the wreckage.
Officials said they would release more details by late afternoon.
A woman who answered a phone listing for Scott Bittner said she was a family friend and refused to comment beyond asking for privacy.
Bittner lived with his wife and two children in Towanda, a small village just outside Bloomington, according to a co-worker who spoke to The Associated Press. He owned a meat processing plant in Eureka, Illinois, carrying on the family's line of work after his dad established another plant in the small city of Chenoa, where Bittner grew up.
"He always told me that he wasn't my boss, that I didn't work for him, I worked with him," said Terry Wertz, who has worked at Bittner's Meat Co. for 15 years.
"He was awful good to me and my family," Wertz said through tears. "If I needed anything, he'd do anything for you."
The plant butchers livestock, including beef, pork, lambs and goats.
Bittner had traveled to Indianapolis for the NCAA tournament using his dad's plane, which he primarily used for business trips, Wertz said.
The aircraft was registered to Make it Happen Aviation LLC of Towanda, Illinois.
DAVID MERCER, Associated Press
A private plane returning from the NCAA basketball tournament in Indianapolis crashed in a central Illinois field on Tuesday, killing all seven people on board, including Illinois State University's associate head basketball coach and a deputy athletics director.
Rescue personnel found no survivors at the site near the city of Bloomington, and a coroner pronounced the seven occupants dead, McLean County Sheriff Jon Sandage said at a news conference. Authorities were withholding identities pending notification of family.
But Illinois State University President Larry Dietz confirmed in an email to students, faculty and staff that associate head basketball coach Torrey Ward and Aaron Leetch, the athletic department's deputy director for external relations, were killed in the early-morning crash.