Who made the list?
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.
(Note: This first appeared in 2014).
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.
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 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.
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.
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.
The dissolution of the Soviet Union left the bulk of Soviet air power in the hands of the new Russian state, and Russia has coasted on this prodigious inheritance for decades.
Altogether, Russia has 1,500 combat aircraft and 400 military helicopters. The bulk of these aircraft, however, are old and have neither been substantially upgraded, nor consistently serviced. MiG-29, Su-27 and MiG-31 fighters that predate the end of the Cold War predominate.
Although the Russian Air Force does not control the country’s ICBM force, it does control strategic nuclear bombers, including aging Tu-95 “Bear”, Tu-22 “Backfire” and Tu-160 “Blackjack” bombers.
The Air Force has finally entered a period of sustained modernization, with new fighters coming online and in development. One example is the Su-35 fighter , a new combat aircraft that combines the agility and versatility of the venerable Su-27 Flanker platform with new, cutting-edge technologies, is entering service in limited numbers.
Russian defense contractors are currently working on the T-50/PAK-FA fighter , which promises to be Russia’s first fifth-generation fighter. Russia is also reportedly working on a new strategic bomber , PAK-DA.
The Russian Air Force has recently adopted a high-profile role as President Vladimir Putin’s rattling sabre, flying extensive missions  near NATO, Swedish and Japanese airspace. These missions are primarily designed as demonstrations of Russian power.
The People’s Liberation Army is an umbrella designation for China’s armed forces, and the two main flying branches of the PLA are the People’s Liberation Army Air Force and the People’s Liberation Army Navy Air Force.
Combined, the PLAAF and PLANAF possess 1,321 fighter and attack aircraft, 134 heavy bombers and tankers and twenty airborne early-warning aircraft. China also operates 700 combat helicopters, mostly of the medium-lift category.
While this may sound like a sizable air force, despite large increases in the defense budget, the majority of those aircraft are obsolete. Only 502 aircraft are modern, variants of the 1980s-era Russian Su-27 Flanker and the indigenously developed J-10 multirole fighter. The remaining 819 fighters date to the 1970s and would not present a serious threat to foreign air forces.
China’s air forces continue to modernize , however, and China’s aviation industry is cranking out new designs quite rapidly. The country is simultaneously developing not one, but two fifth-generation fighters—the heavy J-20 fighter and the smaller J-31 fighter bomber. It is also developing the Y-20 strategic transport and is rumored to be working on a strategic bomber to replace the Xian H-6. Like the American air forces, China is also pushing forward with a variety of unmanned combat aircraft, such as the Dark Sword.
One growth area for Chinese air forces is naval aviation. China’s first carrier, the Liaoning , will likely be followed by additional carriers, although reports concerning capabilities and numbers vary dramatically. The J-15 fighter, a domestic derivative of the Su-27, is currently China’s main carrier fighter, with reports that the multirole J-31 fighter will take on a role similar to the F-35C on American aircraft carriers.
The dark horse on this list is the Japan Air Self Defense Force (JASDF). Japan has more than 300 air superiority and multirole fighters that are finely tuned toward defending the island-nation from threats in the air, land and at sea.
Reflecting the nation’s defense-only military policy, the JASDF is highly specialized towards defensive combat. First and foremost is the mission of air defense: Japan remembers very well what happened the last time it lost air superiority over the Home Islands.
Japanese pilots also practice ground attack against invading forces on Japanese territory and anti-shipping missions against enemy transports and fleets. They do not, however, practice offensive missions such as long-range strike missions.
Japanese pilots are well trained and regarded by their peers. Japanese pilots routinely attend the U.S. Air Force Red Flag exercises, and are kept on their toes by a growing number of scrambles against foreign aircraft nearing Japanese airspace — 533 scrambles in the first half of 2014  alone against a mix of Russian and Chinese aircraft.
Japan buys only the very best air superiority fighters from the United States, having purchased 223 F-15J single-seat and two-seat DJ fighters in the 1980s. These were set to be replaced by the F-22 Raptor; however, Japan was disappointed by U.S. law preventing the F-22 from being exported overseas.
Japan is now set to procure forty-two F-35A Joint Strike Fighters, with the first four aircraft ordered just last month. It is continuing development of the indigenous F-3 fighter project to replace the F-15, under the assumption that future first-line American fighters will be off limits. Meanwhile, F-15J and F-2 fighters are receiving upgrades to boost their air-to-air capability.
To provide early-warning capabilities, as well as command and control, Japan has a fleet of America-sourced aircraft. Japan has four E-767 airborne warning and control system aircraft, and thirteen E-2C Hawkeye airborne early-warning aircraft. The JASDF is set to acquire the latest E-2D Hawkeyes to help deal with the growing number of air intercepts.
Kyle Mizokami is a writer based in San Francisco who has appeared in The Diplomat, Foreign Policy, War is Boring and The Daily Beast. In 2009 he cofounded the defense and security blog Japan Security Watch. You can follow him on Twitter: @KyleMizokami .