The D Check is both costly and time consuming. Many operators sub contract this work to avoid utilising their hangar space which is always needed for smaller work programmes. Equally, some operators use the onset of a D Check programme to change their fleet to new aircraft thus providing a new owner with a lower cost aircraft after the necessary D check is carried out. A typical D check takes between 15,000 and 35,000 man-hours of labour, and can put an aircraft out of service for 15 to 30 days, or more. The total cost averages between $1 million and $2 million.” A typical D check cost is 70% labour and 30% materiel”,