An Air India flight was diverted last week because the crew didn’t raise the landing gear. There were apparently lots of clues that something was terribly wrong but the A320 crew pressed on, climbing to 24,000 feet instead of the normal 35,000 to 37,000 feet and reaching only 230 knots as the plane gobbled huge amounts of fuel to beat the drag of the wheels.
Source: avwebCrew Forgets To Raise Gear