Invicta International Airlines Flight 435 (IM435) was a Vickers Vanguard 952, flying from Bristol Lulsgate to Basel-Mulhouse, which crashed into a forested hillside near Hochwald, Switzerland on 10 April 1973.

[2] When co-pilot Ivor Terry took over, his final approach was based on the wrong beacon and the aircraft crashed into the hillside.

[2] Dorman had previously been suspended from the Royal Canadian Air Force for lack of ability, and had failed his United Kingdom instrument flight rating test eight times.

[8] The aircraft was a Vickers Vanguard 952, registered as G-AXOP, and was chartered by a tour company based in Britain.

In reality, when the crew reported over MN, they were actually in the vicinity of a third beacon, BS, and had already overflown the airport, heading south.

[5] After finishing his telephone call with Zurich, the Basel controller asked if Flight 435 was sure that they had passed beacon BN.

Flight 435 replied that they had a "spurious indication" and that they were joining the localiser, an electronic signal marking the extended centerline of the runway.

The crew then confirmed that they were established on the glide path and localiser, while the controller stated that he could not see them on his radar screen.

[5] At 09:13 UTC, the aircraft brushed the wooded area of a range of hills in Jura and crashed in the hamlet of Herrenmatt, in the parish of Hochwald, some ten miles (16 km) south of the airport and while flying away from it.

Shortly afterwards, a boy from a nearby farm found the survivors, and led them to his house, where his family sheltered and took care of them while waiting for rescue services to arrive.

Most of the passengers and crew were British citizens, among them a group of women from Axbridge in Somerset, United Kingdom.

Captain Dorman had begun his flight training with the Royal Canadian Air Force in 1963, but it was soon discontinued owing to his insufficient aptitude for flying.

He had begun his flight training with the Royal Air Force in October 1944 and had been a military pilot since 1947, with experience flying Lancaster, Shackleton, Varsity and Valetta aircraft.

At the time of the accident, the aviation regulations in the United Kingdom didn't require the presence of a Cockpit Voice Recorder in every transport-category aircraft.

As Basel was located in a mountainous area, this limited visibility could be dangerous as the aircraft, like most airliners of its era, was not equipped with a Ground Proximity Warning System (GPWS).

[5][page needed] The inclement weather conditions, and the fact that the modulation of beacons MN and BN didn't comply with ICAO requirements, caused every crew on every flight approaching Basel at the time to have some difficulties.

Because it was not reliable, it was essential to monitor the aircraft's position by additional static-free navigational aids, or by radar from the ground.

[5] On the 50th anniversary of the disaster, services of remembrance were held at churches in Congresbury, Wrington, Axbridge and Cheddar.