Andrew Thompson, 37, and John MacKinnon, 53, died in May 2015 when the G-Rick Beech Baron aircraft crashed near the village of Abernyte in Perthshire.
There was low cloud and heavy rain in the area at the time - described as instrument meteorological conditions (IMC) - meaning the pilot had to fly primarily by reference to instruments.
An Air Accidents Investigation Branch (AAIB ) report concluded a mix-up of distances between the onboard GPS system and distance measuring equipment (DME) from the runway caused the pilot to start his descent too early.
Investigators said: “The aircraft collided with high ground 6.7 nm (nautical miles) to the west of Dundee Airport whilst conducting an instrument approach to runway 09 in IMC.
“Evidence indicates that the pilot probably mistook the distances on his GPS, which were from the NDB (non directional radio beacon), as DME distances from the threshold of runway 09 and therefore commenced his descent too early.
“Anecdotal evidence suggests that mistaking GPS distance from the ‘DND’ NDB with DME distance is a common error made by pilots. The operator of Dundee Airport is taking safety actions, intended to prevent a recurrence.”
The AAIB report added: “Dundee Airport has high ground on the approach, an offset NBD and no radar surveillance.
“This combination can result in a pilot inadvertently letting down to the NDB instead of the runway in IMC conditions, with no effective ‘safety net’.
“Aviation should, however, in so far as possible, be an ‘error tolerant’ environment.”
The airport operator, Highlands and Islands Airports (HIAL), has commissioned a safety survey to consider relocating the remote NDB and other measures.
All incoming aircraft now also hear the broadcast: “Pilots are reminded that the NDB and DME are not co-located”.
The aircraft was travelling from Inverness to Dundee for scheduled maintenance checks when it lost contact with air traffic controllers just a few miles west of the hub.
The wreckage of the small plane was found near the village of Abernyte about four hours after it went missing.
Mr Thompson was from Chester in Cheshire, and MacKinnon from Ross-shire.