The litigants allege that a design flaw by Boeing and Honeywell allowed the fuel supply to be cut off, causing complete engine failure

The families of four passengers killed when a UK-bound Air India flight crashed earlier this year have filed a lawsuit against US aerospace companies Boeing and Honeywell, the NDTV website reported on Thursday. 

The 787-8 Dreamliner carrying 242 people crashed into a residential area in Ahmedabad, India shortly after takeoff on June 12. Only one person on board survived. Nineteen people on the ground were also killed. 

The lawsuit, filed on Tuesday in the Delaware Superior Court, alleges that the two companies were negligent and that a faulty fuel cutoff switch caused the accident, according to the report.

A preliminary report by India's Aircraft Accident Investigation Bureau found that cockpit fuel switches had been switched off seconds after takeoff, which shut down both engines. The litigants believe this was caused by a design defect that "allowed for inadvertent cutoff of fuel supply and total loss of thrust necessary to propel" the plane, according to a BBC report.

They also allege that Honeywell and Boeing, which manufactured and installed the switch respectively, were aware of the risk, particularly after the US Federal Aviation Administration warned about disengaged locking mechanisms on several Boeing aircraft in 2018.

The complaint stated that by placing the switch directly behind the thrust levers, Boeing essentially ensured that normal cockpit activity could result in an inadvertent fuel cutoff. The litigants also allege the companies failed to warn airlines that these switches needed urgent checks or repairs and did not provide replacement parts to fix the issue, according to the BBC.

In June India's aviation regulator ordered fuel system checks on all domestic aircraft made by Boeing.

The US Federal Aviation Administration (FAA) has said the fuel control switches in Boeing aircraft are safe. 

In a letter to employees in July, Air India CEO Campbell Wilson said a preliminary report had found no mechanical or maintenance issues with the aircraft or engines.