Pre-Flight Inspection
The captain believed the daily inspection had been completed earlier that morning and was not required again. They also did not consider a crew change external inspection necessary. Consequently, the captain performed an abbreviated walk-around without referencing any checklist. The first officer (FO) removed engine bungs and static port covers but could not reach the pitot covers on the nose, asking the captain to remove them. The captain agreed but subsequently forgot. The FO, seeing 'remove before flight' tags in a bag, incorrectly assumed those were attached to the pitot covers. No further discussion occurred, and the pitot covers remained in place.
Operator’s Guidance
The operator’s Flight Crew Operating Manual (FCOM) required a terminating check if the aircraft was unattended for over 60 minutes, but did not specify checks upon return. The operator expected pitot covers to be fitted when on the ground for over 60 minutes, yet the securing procedure stated they should be fitted only after the last flight, creating confusion. Additionally, the final '4321' visual check did not include verifying that pitot covers were removed.
Poor Visibility
Night-time conditions and heavy rain likely prevented the flight crew from detecting the pitot covers during taxi. Air traffic control, other pilots, and ground staff also had no opportunity to see the covers. The pitot covers remained undetected.
Airspeed Indications During Take-off
During the take-off run, the airspeed indicators showed slowly increasing speeds, which the crew did not recognize as erroneous. They believed airspeed could still increase with pitot covers on. The captain decided to continue take-off after realizing the airspeed was unreliable, likely near V1. Had the crew detected the issue earlier, a rejected take-off might have been possible.