One of the chief reasons may be that the KC-390 cannot always reach areas that the hardier C-130 Hercules and its current upgrade C-130J Super Hercules can with its four-engine turboprop configuration.
Brazilian aviation manufacturer Embraer opted for jets instead of turboprop engines for its KC-390, contender for an estimated 700 potential replacements for ageing C-130s worldwide but that strategy means the KC-390 may be limited in landing and taking off in rough terrain, analysts said.
Embraer sought buyers for the aircraft at Rio de Janeiro's LAAD defense and security exhibition this month but didn't say if it secured any contracts.
Teal Group defense analysts see the KC-390 as more of a straight cargo plane than the C-130, with higher load capacity, modern features like fly-by-wire and a faster cruising speed, Defense Industry News said, citing Flight International.
However, the C-130's use of turboprops is better for avoiding foreign object damage from unimproved landing strips and for low altitude operation, which makes them better suited to roles like Special Forces support, Flight International said.
The KC-390's first flight is scheduled for next year, which will determine its production and delivery timeline. The KC-390 is likely to be about $12 million cheaper than the C-130J, which comes with a price tag of about $62 million.
Despite being more expensive the C-130J has secured more than 300 orders worldwide. More than 60 countries would still use the old workhorse and some have opted for avionics and hardware upgrades on the old planes rather than turning to alternatives. The Hercules aircraft family claims the longest continuous production run of any military aircraft.
Embraer says it can compete against most rivals including the C-130J. The Brazilian planemaker has been recruiting international partners as part of a strategy to boost the competitive edge for its contender KC-390.
The old C-130 beat competition from Boeing B-52 Stratofortress, Soviet/Russian Tupolev Tu-95 and Boeing KC-135 Stratotanker. Lockheed Martin's updated C-130J Super Hercules can perform in-flight refueling, air-to-refueling and tanking. Embraer says it hopes to give its KC-390 all those features plus more.
Embraer says its aircraft will command a lift of 23 tons against 20 tons for most competitors, which include the larger Airbus A400M and Russian and Chinese aircraft.
Embraer is extending its efforts and markets by crafting a jet-powered medium transport with a cargo capacity of around 23 tons, that can be refueled in the air, and can provide refueling services to other aircraft by adding dedicated pods, the Defense Industry Daily said on its website.
"The KC-390 has now become a multinational effort, and may be shaping up as the C-130′s most formidable future competitor," Defense Industry Daily said.
The Boeing Co. and Embraer announced an agreement to collaborate on the KC-390 aircraft program.
Boeing says it can bring to Embraer its experience in military transport and air refueling aircraft, as well as knowledge of potential markets for the KC-390.
Some of the transport plane's structural parts will come from Portuguese companies after an agreement signed by Embraer and OGMA, or Industria Aeronautica de Portugal, and Empresa de Engenharia Aeronautica.
The Brazilian company AEL Sistemas, based in Porto Alegre, is another partner supplying components for the KC-390.