Qualifying the five most powerful air forces in the world is certainly a difficult and challenging proposition. There are large, well-trained and well-equipped air forces that are obvious candidates for such a list. Then there are less-obvious candidates—like Russia. The Russian Air Force, while plane-for-plane older than many air forces, has numbers, the ubiquity of the largest country by size on Earth, a modernization plan and nuclear weapons. It cannot be ignored, and thanks to Putin and his repeated sorties near NATO and Japanese air space, it certainly won’t be. China is in many ways similar.After that, however, the road gets murky. Vulnerabilities become apparent. There are air forces that are well equipped and trained, but for budgetary reasons, are too small to adequately fulfill national roles and requirements (think all of Europe.) There are also air forces that are magnificently equipped, but poorly trained. (Think virtually all of the Middle East.) For the purpose of this article, we’ll judge air forces by the following criteria: size, influence and doing the best job of matching capabilities to the mission. United States The U.S. Air Force The preeminent air arm of the United States, the U.S. Air Force (USAF), is the primary service responsible for air and space missions. It manages everything from intercontinental ballistic missiles to X-37 space planes to A-10 Thunderbolt tank killers. It coordinates military space launches, airdrops of Army paratroopers and drops bombs on ISIS insurgents. (Recommended: The U.S. Army's 5 Most Lethal Weapons of War) The USAF operates 5,600 aircraft of all types, including F-22 Raptors, F-35, F-15 and F-16 fighters. It operates B-2, B-1 and B-52 strategic bombers, as well as C-5, C-17 and C-130 airlifters. It operates these aircraft from bases in the continental United States and overseas bases from the United Kingdom to Japan. The Air Force has roughly 312,000 active-duty members, coming in just behind the People’s Liberation Army Air Force, and yet it operates more planes than the PLAAF. The USAF was the first air force worldwide to fly stealth combat aircraft, the first to fly fifth-generation fighters, and the first to commit to an all-stealth combat aircraft force. The USAF plans on preserving its edge by purchasing 1,763 F-35s and up to 100 optionally manned Long-Range Strike Bombers. Unmanned aerial vehicles, increasingly with stealthy profiles and attack capabilities, will gradually represent a larger proportion of the overall aircraft fleet. (Recommended: Russia's Deadly Su-35 Fighter) The USAF also manages two legs of the U.S. nuclear triad, including 450 intercontinental ballistic missiles and the strategic bomber force. The U.S. Navy and Marine Corps Worthy of separate mention due to their size and capabilities, the U.S. Navy and Marine Corps are combined the world’s second-largest air force, with a total of over 3,700 aircraft of all types. This includes 1,159 fighters, 133 attack aircraft, 172 patrol aircraft, 247 transports and 1,231 helicopters. The aircraft of the U.S. Navy are responsible for protecting the U.S. fleet and conducting air missions from and often over the world’s oceans and seas. Most of the aircraft of the Navy and Marine Corps operate from ships at sea, a difficult and dangerous job that requires a high level of training and proficiency. (Recommended: The Russian Air Force's Secret Weapon) The most visible aspect of U.S. naval aviation are the carrier air wings that fly off eleven nuclear-powered aircraft carriers. Each wing typically consists of around sixty aircraft divided into three squadrons of F/A-18 Hornets and Super Hornets, one E-2C Hawkeye airborne early-warning squadron, one EA-18G Growler electronic warfare squadron, and one helicopter squadron. Other aspects of naval aviation include the helicopters that fly off U.S. Navy cruisers, destroyers and other surface ships, P-3 Orion and P-8 Poseidon maritime control aircraft, and variants of the P-3 that conduct electronic surveillance missions. US navy aviation also contributes to the U.S. strategic nuclear force, flying TACAMO (Take Charge And Move Out) aircraft whose mission is to provide command and control in the event of a nuclear war. U.S. Marine Corps aircraft are counted under the Navy total and serve on Navy ships, but are oriented towards Marine combined air-ground operations, with an emphasis on supporting marine ground forces.