LOT Polish Airlines Flight 7 increased engine wear, since the engines were under greater load. NK-8-4 engines were not reliable enough. Warranty service life was only 5000 hours, and about half of LOT engines failed after 2000–3000 hours. Because of this, Polish pilots often called the Il-62 "flying coffins". In spite of the low reliability, the airline decided to increase overhaul life intervals to reduce the frequency of repairs, which were carried out in Soviet factories and quite expensive. LOT sent a letter to the Ilyushin Design Bureau containing the results of a test in which it was found that the engines could operate normally
National brand local- or private-branded product. National brand A national brand is the brand of a product that is distributed nationally under a brand name - owned by a producer or distributor - as opposed to local brands (products distributed only in some areas of a country), and to private-label brands (products that carry the brand of the retailer rather than the producer.) National brands compete with local and private brands. National brands are produced by, widely distributed by, and carry the name of the manufacturer. On the other hand, marketing and advertising may give consumers the impression that a national-brand product