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LITTLE ROCK, Ark. - A plane carrying two Oklahoma State University basketball coaches and a couple ferrying them to Arkansas for a recruiting trip was inspected and its muffler repaired about a week before it crashed, killing all four people on board, according to a report released this week.

The single-engine plane had an annual inspection on Nov. 8, 2011 — a little more than a week before it crashed on Nov. 17, 2011, near Perryville, Ark., about 70 kilometres northwest of Little Rock, according to a National Transportation Safety Board report dated Thursday and sent to reporters Friday.

"During the annual inspection, the mechanic noted that the muffler was inspected, removed, weld repaired, and reinstalled," the report said.

OSU women's basketball coach Kurt Budke and assistant coach Miranda Serna died in the crash on their way from Stillwater, Okla., to Little Rock, Ark., where they planned to scout prospective recruits. The pilot, former Oklahoma lawmaker Olin Branstetter, and his wife, Paula Branstetter, also died.

The report did little to answer questions about why the plane crashed, but instead provided details about the plane and pilot's log books. A probable cause report is expected to come out in about three months.

NTSB investigator Jason Aguilera did not respond to a phone message left Friday seeking comment.

Weather has been ruled out as a factor, but it's still not clear whether the 82-year-old pilot had any medical issues that could have contributed to the crash. Autopsy results showed Branstetter's death was "essentially instantaneous," but a medical examiner couldn't determine much else because his remains were in bad shape.

Investigators said most of the plane's cockpit instruments were unreadable, unreliable or destroyed.

The muffler didn't show any "preimpact anomalies," according to the report. "No preimpact anomalies with the airframe or engine were found which would have precluded normal operation," the report said.

The NTSB report also confirmed what Branstetter's family said just days after the crash: He flew a lot.

Branstetter's records showed he logged more than 2,200 flying hours, including more than 350 hours in the plane that crashed, according to the report.

A flight log recovered from the wreckage contained flights on Oct. 25, 2011, Nov. 16, 2011, and a partial entry on the day of the crash.

The report also noted that Branstetter, an OSU graduate, "volunteered his flight services to assist with the athletic department's recruiting efforts, was not compensated for his flight time, and was not contracted by the university."

About a year after the crash, Oklahoma State regents approved tougher oversight of the airplanes that any employee uses use on official business. The policy requires an aviation consultant to approve any private aircraft and the pilot.

News from © The Associated Press, 2013