He lost control of his microlight while attempting to land at an airstrip near Edenbridge, Kent, on 16 July last year.
Investigators said his decision to fly at 15:30 BST was when conditions were more likely to be turbulent than later.
They said he may have been influenced by the fact the airstrip operator took time to help him prepare the aircraft.
"He may have felt some pressure to fly," the Air Accidents Investigation Branch (AAIB) report found.
A nearby dog walker described how the Pegasus Quantum 15 was "a bit wobbly" and travelling "too fast and at too acute an angle" as it came in to land at East Haxted Farm Airstrip.
The AAIB said the pilot encountered "very rough air" which caused him to veer off course and abort the landing.
The pilot, who was not identified by the AAIB, suffered chest and hand injuries when the microlight became entangled in the branches of an oak tree about 15ft (4.6m) above a field near Lingfield Road.
He was freed after several hours by fire crews using using ladders, lines and a winch.
He had held a private pilot's licence since 1997 and although he was "reasonably experienced" he was "not in current flying practice" and had flown for just two hours in the 90 days leading up to the crash, the report said.
Civil Aviation Authority data from December 2015 shows  he was one of the country's oldest pilots, as just 13 people aged 89 or older held pilot licences at that time.
Holders of his type of licence aged over 50 must renew a medical certificate every 12 months to keep flying.

Mark Jones, 45, of Cwmbran, Torfaen, has pleaded not guilty to murder at his trial at Newport Crown Court.
The jury heard Mr Jones changed his story during a series of police interviews over a number of months.
Initially, Mr Jones said he tripped over a toy and dropped Amelia Jones the day before she was taken to hospital.
He told police he dropped his granddaughter on 16 November 2012, but then said in a later interview that another person, who cannot be named for legal reasons, dropped her the following day while "messing" with their phone.
The trial has been told that baby Amelia suffered a fractured skull, brain swelling and eight rib fractures.
She had been injured at least three different times, the court heard.
The trial continues.

The device was discovered last week, southeast of Tucson, Arizona, when agents spotted a group of men scattering as they approached.
A closer look turned up two bundles of cannabis weighing a combined 47lb (21kg), which had yet to be launched.
The catapult was dismantled on the Mexican side. No arrests were made.
About 650 miles of the 1,100-mile (1,770km) border is covered by some sort of wall or fence.
Donald Trump has committed himself to building more walls, but drug traffickers have in recent years turned to increasingly creative means of getting their product over, including drones, car ramps, and air cannons.
Traffickers have also made extensive use of tunnels under the border. In March, authorities uncovered a 380m tunnel that ran from a restaurant in Mexico to a house in California.

Tigers were awaiting official clearance from the French Rugby Federation and the 30-year-old, who has won 35 Test caps, is now able to cover for injured duo Manu Tuilagi and Matt Toomua.
Head coach Aaron Mauger said: "We are missing two big players in midfield.
"We're very happy to be able to bring in a player of Maxime's style, quality and experience."
A 90-year-old pilot who was seriously hurt when his microlight crashed in to a tree may have felt under pressure to fly, according to an accident report.
[NEXT_CONCEPT]
A man accused of murdering his five-week-old granddaughter said someone else dropped her the night she was taken to hospital, a court has heard.
[NEXT_CONCEPT]
US border patrol agents have found a medieval-style catapult mounted on the border wall with Mexico, designed to launch bundles of drugs into the US.
[NEXT_CONCEPT]
Leicester have completed the signing of France centre Maxime Mermoz from Toulon until the end of the season.