Aviation regulator DGCA on Tuesday appeared to keep the door open on the possibility of human error while noting that no abnormal parameters were observed in Air India’s Boeing 787-8 Dreamliner that faced a fuel-control switch glitch last week.

The detailed sequence of events issued by the DGCA on what transpired on the Bengaluru-London flight suggests that the Air India plane took off on February 1 despite the fuel-control switch having malfunctioned twice after the airline’s engineering team told the crew to avoid “unnecessary contact with the switch”.

The DGCA, while quoting the engineering team’s observations, said that “applying external force in an incorrect direction caused the switch to move easily from ‘RUN’ to ‘CUT OFF’, due to the angular base plate allowing slip when pressed improperly with finger or thumb”.

The functioning of the fuel-control switch is in focus following the crash of Air India’s Boeing 787-8 Dreamliner in Ahmedabad last June that killed 260 people. The preliminary probe report had said the fuel supply had cut off soon after take-off.

Referring to the February 1 flight in its statement on Tuesday, the aviation regulator said no abnormal engine parameters, cautions, warnings, or related system messages were observed when the engine was restarted or thereafter.

“The operating crew member was briefed on the observation, unnecessary contact with the switch was avoided, and engine indications and alerting systems were closely monitored by the crew for the remainder of the flight. The flight was completed without incident,” the statement said.

The DGCA said the crew initially faced an issue with the fuel-control switch while the engine was being switched on in London.

“During engine start in London, on two occasions crew observed that the fuel control switch did not remain positively latched in the ‘RUN’ position when light vertical pressure was applied,” the statement said.

“On the third attempt, the switch latched correctly in ‘RUN’ and subsequently remained stable. Before continuing with the rest of the procedure, a physical verification was performed by the crew to confirm that the switch was fully and positively latchedin the ‘RUN’ position,” the DGCA said.

“Run” and “Cut Off” are used to start or shut down engines, respectively.

After the incident was reported, Air India’s engineering team made certain observations based on Boeing-recommended checks to establish the serviceability of the fuel-control switch.

Citing the team’s observations, the DGCA said both the left and right switches were checked and found satisfactory, with the locking tooth/ pawl fully seated and not slipping from Run to Cut Off.

“When full force was applied parallel to the base plate, the switch remained secure,” the DGCA said.

The DGCA said that after landing in Bengaluru, the crew reported the defect and Air India referred the matter to Boeing for further guidance. On the basis of the communication with Boeing, the DGCA said the pull-to-unlock force was checked on the fuel control-switch using the recommended procedure.

“In all cases the pull-to-unlock force was found within limits. These inspections were carried out in the presence of DGCA officers,” the statement said.

The DGCA advised Air India to circulate among its crew members the procedure recommended by Boeing for the operation of the fuel Cut Off switch.

A pilot said on the condition of anonymity that the DGCA had willy-nilly accepted there was a defect as the fuel-control switch became stable after the third attempt. “Why did it happen the first time? Why did the fuel-control switch move from Run to Cut Off two times?” the pilot asked.

Air India did not comment on the DGCA statement.

According to sources, Air India’s senior vice-president for flight operations, Manish Uppal, has told Boeing 787pilots that the airline hasinitiated a fleet-wide re-inspection of the aircraft’s fuel-control switches.