That is what Kalitta bought 706 from Delta for to begin with. Then he became a willing participant of the scam by letting Baltia claim: YPSILANTI, Mich., Oct. 23, 2014 /PRNewswire/ -- Baltia Air Lines (BLTA) announced today that the C4 Check of its B747 Aircraft has been signed off by Kalitta Maintenance.
The C4 check, sometimes referred to as a D Check, is the most comprehensive inspection that an airliner undergoes, occurring every six years. The inspection involves structural and systems testing using X-ray, ultrasound, and other methods.
This is by far the most comprehensive and demanding check for an airplane. It is also known as an IL or "heavy maintenance visit" (HMV). This check occurs approximately every 6 years.[4] It is a check that more or less takes the entire airplane apart for inspection and overhaul. Even the paint may need to be completely removed for further inspection on the fuselage metal skin. Such a check can generally take up to 50,000 man-hours and 2 months to complete, depending on the aircraft and the number of technicians involved. It also requires the most space of all maintenance checks, and as such must be performed at a suitable maintenance base. The requirements and the tremendous effort involved in this maintenance check make it by far the most expensive, with total costs for a single D check in the million-dollar range.
Because of the nature and the cost of such a check, most airlines — especially those with a large fleet — have to plan D checks for their aircraft years in advance. Often, older aircraft being phased out of a particular airline's fleet are either stored or scrapped upon reaching their next D check, due to the high costs involved in comparison to the aircraft's value. On average, a commercial aircraft undergoes three D checks before being retired. Many maintenance, repair and overhaul (MRO) shops claim that it is virtually impossible to perform a D check profitably at a shop located within the United States. As such, only a few of these shops offer D checks.[citation needed]
Given the time requirements of this check, many airlines use the opportunity in order to also make major cabin modifications on the aircraft, which would otherwise require an amount of time that would have to put the aircraft out of service without the need for an inspection. This may include new seats, entertainment systems, carpeting, etc.