C-130J, is still the yardstick against which newer military transport aircraft designs are measured. Although larger, smaller and faster designs have been proposed for many years, the C-130 continues to improve at a rate that keeps it in production. "Strategic" cargo aircraft became an important class of their own starting with the Lockheed C-5 Galaxy in the 1960s and a number of similar Soviet designs from the 70s and 80s, and culminating in the Antonov An-225, the world's largest aircraft. These designs offer the ability to carry the heaviest loads, even main battle tanks, at global ranges. The Boeing 747 was originally designed to the same specification as the C-5, but later modified as a design that could be offered as either passenger or all-freight versions. The "bump" on the top of the fuselage allows the crew area to be clear of the cargo containers sliding out of the front in the event of an accident. When the Airbus A380 was announced, the maker originally accepted orders for the freighter version A380F, offering the second largest payload capacity of any cargo aircraft, exceeded only by the An-225. An aerospace consultant has estimated that the A380F would have 7% better payload and better range than the 747-8F, but also higher trip costs. Starting May 2020 Portuguese Hi Fly started charting cargo flights with an A380, carrying medical supplies from China to different parts of the world in the response to the Covid-19 outbreak. It allows almost of cargo between the three decks. In November 2020 Emirates started offering an A380 mini-freighter, which allows for 50 tons of cargo in the belly of the plane. Cargo aircraft types Nearly all commercial cargo aircraft presently in the fleet are derivatives or transformations of passenger aircraft. However, there are three other methods to the development of cargo aircraft. Derivatives of non-cargo aircraft Many types can be converted from airliner to freighter by installing a main deck cargo door with its control systems; upgrading floor beams for cargo loads and replacing passenger equipment and furnishings with new linings, ceilings, lighting, floors, drains and smoke detectors. Specialized engineering teams rival Airbus and Boeing, giving the aircraft another 15–20 years of life. Aeronautical Engineers Inc. converts the Boeing 737-300/400/800, MD-80 and Bombardier CRJ200. Israel Aerospace Industries’ Bedek Aviation converts the 737-300/400/700/800 in about 90 days, 767-200/300s in about four months and 747-400s in five months, and is